UC-NRLF 


SB    317    153 


Combustion  of  Coal 


AND  THE 


Prevention  of 


BARR 


Combustion  of  Coal 

and  the  Prevention  of  Smoke 

A  PRACTICAL  TREATISE  FOR 

Engineers,  Firemen  and  All  Others  Interested 

in  Fuel  Economy  and  the  Suppression  of 

Smoke  from  Stationary  Steam-Boiler 

Furnaces,  and  from  Locomotives 

Contains  nearly  500  questions,  with  their  answers, 

covering  everything  relating  to  combustion, 

heat,  and  steam  generation 


WILLIAM  M.  BARR,  M.E. 

Author  of  "Boilers  and  Furnaces,"  etc. 


FULLY  ILLUSTRATED — FIFTH  EDITION 


NEW   YORK 

THE  NORMAN  W.   HENLEY  PUBLISHING  COMPANY 
132  NASSAU  STREET 

1913 


2-5 

133 


COPYRIGHTED,    1918 
BY  THE  NORMAN  W.  HENLEY  PUBLISHING  CO. 


COPYRIGHTED,  1900,  BY  WILLIAM   M.  BARR 


PREFACE. 


THIS  edition  of  combustion  of  coal  is  so  entirely  differ- 
ent from  my  former  treatise  that  it  is  to  all  intents  a  new 
book.  Much  of  the  original  material  has  been  retained, 
but  worked  over  and  presented  in  new  form.  The  aim  of 
the  writer  is  sufficiently  indicated  by  the  title  page,  in 
which  it  will  be  seen  that  the  subject  has  special  refer- 
ence to  the  economical  and  smokeless  combustion  of  or- 
dinary fuels  in  the  generation  of  steam. 

The  best  book  for  practical  and  busy  men  is  the  one 
which  is  nearest  complete  in  itself.  In  view  of  this  fact, 
the  writer  has  included  in  these  pages  much  collateral 
information  and  useful  data,  not  always  bearing  directly 
upon  furnace  combustion,  in  the  belief  that  such  informa- 
tion would  be  helpful  and  gladly  received  by  those  wishing 
to  acquire  a  broader  knowledge,  including  all  the  facts 
relating  to  the  subject  of  combustion  in  general. 

Unavoidable  repetitions  occur  in  this  book,  as  it  was 
thought  improbable  that  it  would  in  all  cases  be  studied 
systematically  from  end  to  end,  in  which  case  the  subject- 
matter  might  have  been  shortened  by  means  of  cross  refer- 
ences. In  view  of  the  probability  that  this  book  will  be 
commonly  used  as  its  contained  information  is  required, 
which  will  then  be  sought  out  by  means  of  the  index, 
it  was  thought  best  to  make  each  answer  as  complete  as 
possible,  and  without  reference  to  the  fact  that  the  same 
data  occurred  elsewhere  in  this  volume. 

There  has  been  a  somewhat  unlooked-for   demand  for 


PREFACE. 

s  this,  mainly  from  locomotive  engineers  and 
firemen,  by  reason  of  the  insistance  on  the  part  of  the  man- 
agement of  the  more  important  railway  lines  that  their 
locomotive  engineers  and  firemen  shall,  among  other  re- 
quirements, undergo  a  satisfactory  examination  in  the  prin- 
ciples of  the  combustion  of  coal  and  of  the  laws  governing 
the  prevention  of  smoke ;  this,  with  a  view  to  securing  a 
better  or  more  rational  method  of  firing,  as  well  as  leading 
up  to  the  abatement  of  the  smoke  nuisance,  which  in  many 
localities  has  become  almost  unbearable.  For  this  pur- 
pose my  former  treatise  was  wanting  in  practical  detail, 
and  is  a  reason  for  a  new  presentation  and  restatement  of 
this  important  subject. 

The  publishers  have  had  marked  success  in  the  several 
catechisms  issued  from  their  press,  and  it  was  their  desire 
that  this  book  should  conform  in  size  and  method  of  pres- 
entation with  their  other  publications.  But  aside  from 
this,  no  apology  is  needed,  for  no  form  of  presentation  is 
so  popular  with  practical  and  busy  men  as  the  simple  one 
of  question  and  answer. 

The  questions  are  intended  to  cover  every  detail  relating 
to  the  economic  combustion  of  such  fuels  as  are  employed 
in  steam  engineering.  The  answers  are,  so  far  as  the 
writer  is  able  to  prepare  them,  scientifically  accurate. 
The  authorities  quoted  in  my  former  treatise  have  been 
used  in  this,  and  in  addition  thereto  free  use  has  been  made 
of  the  several  excellent  papers  by  Professor  Thorpe,  on 
fuels,  heat,  combustion,  etc.  Acknowledgment  is  also 
made  of  materials  selected  from  the  writings  of  such 
authorities  as  Hoadley,  Snow,  Kent,  Bell,  Thurston,  Sin- 
clair, Barrus,  Carpenter,  and  others. 

WILLIAM  M.  BARR. 


CONTENTS. 


CHAPTER.  PAGE. 

I.— Fuels,        , 9 

II. — Some  Elementary  Data, 48 

III.— The  Atmosphere, 68 

IV. — Combustion,       ..........  83 

V. — Products  of  Combustion, 103 

VI. — Heat  Developed  by  Combustion,      .                 ...  140 

VII. — Fuel  Analysis, 160 

VIII.— Heating  Power  of  Fuels, 178 

IX. — Steam  Generation, 201 

X. — Stationary  Furnace  Details,      .         .         .         .         .         .215 

XI. — Locomotive  Furnace  Details, 249 

XII. — Chimneys  and  Mechanical  Draft,     .....  309 

XIII. — Spontaneous  Combustion,         ......  330 


COMBUSTION    OF   COAL 


CHAPTER  I. 

FUEL. 

Q.  What  is  meant  by  term  fuel  ? 

Fuel  expresses  in  a  word  and  in  general  terms  any  sub- 
stance which  may  be  burned  by  means  of  atmospheric  air, 
with  sufficient  rapidity  to  evolve  heat  capable  of  being 
applied  to  economic  purposes.  The  economic  value  of  any 
fuel  will  depend  upon  its  heating  power.  The  two  ele- 
ments contributing  this  property  to  fuel  are  carbon  and 
hydrogen.  The  more  important  varieties  of  fuel  include 
wood,  peat,  lignite,  coal,  natural  and  producer  gas,  and 
petroleum. 

Q.  Of  what  does  fuel  consist? 

All  fuel  consists  of  vegetable  matter  or  the  products 
of  its  alteration.  The  elementary  constitution  of  fuel  is 
consequently  much  the  same,  carbon,  hydrogen,  oxygen, 
nitrogen,  and  inorganic  matter  that  constitutes  the  ash. 
The  gradual  process  of  woody  tissue  into  anthracite  is 
shown  in  the  following  analytical  results  in  which  the 
hydrogen  and  oxygen  percentages  are  based  on  that  of 
carbon : 


10 


COMBUSTION   OF   COAL. 
TABLE  i. — COMPOSITION  OF  FUEL. 


Fuels. 

Carbon. 

Hydrogen. 

Oxygen. 

Wood 

IOO 

12  1  8 

go  07 

Peat  

IOO 

Q  8^ 

c  c  67 

Lignite  

IOO 

8.^7 

42  42 

Bituminous  coal  ....          

IOO 

6  12 

21   2^ 

Anthracite  . 

IOO 

2  84 

I    7A 

i.  /q. 

The  following  table  shows  the  chemical  alterations  in 
approximate  percentages  of  carbon,  hydrogen,  and  oxygen 
as  occurring  in  the  different  fuels  : 


TABLE  2. — COMPOSITION  OF  FUEL. 


Fuels. 

Carbon. 

Hydrogen. 

Oxygen. 

Wood  .              

C2  6«; 

c  2C 

42  IO 

Peat  

60  44 

5  06 

oa  60 

Lignite  

66  06 

5  27 

27  76 

Bituminous 

76  18 

*  64 

1  8  07 

Semi-anthracite 

QO  5O 

c  QC 

44O 

Anthracite 

02  8^ 

^  06 

•3      IQ 

Q.  What  is  coal  ? 

Coal,  as  defined  by  Dr.  Percy,  is  a  solid  stratified  mineral 
substance,  black  or  brown  in  color,  and  of  such  a  nature 
that  it  can  be  economically  burnt  in  furnaces  or  grates. 

Our  acquaintance  with  the  chemistry  of  coal  is  almost 
entirely  confined  to  a  knowledge  of  its  ultimate  composi- 
tion. We  know  it  to  be  made  up  of  variable  proportions 
of  carbon,  hydrogen,  oxygen,  and  nitrogen ;  but  there  are 
reasons  for  believing  that  in  bituminous  coals  there  exist 
ready  formed  definite  compounds,  at  all  events,  of  hydro- 
gen and  carbon. 

Besides  these  strictly  organic  ingredients  coals  contain 
varying  amounts  of  what  must  be  regarded  as  impurities 
in  the  shape  of  mineral  matters,  which  constitute  the  ash, 


CLASSIFICATION    OF   COAL.  II 

and  pyrites  or  bisulphide  of  iron.     Sulphur  in  the  free 
state  is  sometimes  present  in  coal. 

Q.  What  is  the  commercial  classification  of  coals  ? 

The  coals  of  the  United  States  range  in  hardness  from 
the  dense  anthracite  through  all  gradations  to  the  soft, 
easily  crumbled  lignite.  The  commercial  classification 
separates  them  broadly  into  hard  and  soft  coals,  or  into 
anthracite  and  bituminous  coals.  This  classification  in- 
cludes among  the  anthracite  coals  the  semi  or  gaseous  an- 
thracites. The  bituminous  coals  include  semi-bituminous, 
caking,  non- caking,  cannel,  block,  and  other  varieties,  as 
well  as  all  the  gradations  of  lignite,  a  faulty  classification, 
but  one  which  works  little  or  no  inconvenience,  because 
orders  for  bituminous  coals  are  usually  placed  in  open 
market  designating  whether  intended  for  coke-making, 
gas-making,  blacksmith  and  forge  work,  boiler  furnaces,  or 
other  need  of  the  customer;  large  orders  not  infrequently 
specifying  the  locality  if  not  the  particular  mines  from 
which  the  coals  are  to  be  shipped. 

Q.  What  are  the  physical  properties  of  the  coals  in 
Gruner's  classification  ? 

In  Gruner's  classification  of  coals  the  following  physical 
properties  predominate : 

1.  Anthracite,    or    lean    coals;    burning  with   a   short 
flame;  having  a  black  color,  and  a  specific  gravity  of  1.33 
to  1.4.     These  coals  form  the  transition  to  true  anthracite. 
On  coking  they  yield  82  to  90  per  cent  fritted  or  pulveru- 
lent coke,   and    12  to  18   per  cent  of  gas.     Evaporative 
factor,  9  to  9. 5 . 

This  coal  adapted  for  domestic  use. 

2.  Caking  coals  (fat  coals)  burning  with  a  short  flame; 


12  COMBUSTION   OF   COAL. 

color,  black,  shining,  often  with  lamellar  structure.  Spe- 
cific gravity,  1.30  to  1.35.  Yields  74  to  82  per  cent  fairly 
hard  coke,  caked  together  very  densely,  and  12  to  15  per 
cent  gases.  Evaporative  factor,  9.2  to  10. 

Adapted  for  coking  and  for  heating  steam  boilers. 

3.  Caking  coals  proper,  or  furnace  coals.     Burning  with 
longer  flame;  color,  black,  shining,  lustre  more  marked; 
these  coals  swell  under  the  action  of  heat  more  than  those 
of  classes  i  and  2.     Specific  gravity,  1.30.     Yields  68  to 
74  per  cent  caked  fairly  dense  coke,  and   13   to    16   per 
cent  gases.     Evaporative  power,  8.4  to  9.2. 

Adapted  for  coking  and  smithy  use. 

4.  Caking  coals,  long  flaming  (gas  coal).      These  coals 
burn  with  a  long  flame.     Color,  dark,  high  lustre.      Coals 
hard  and  tough.     Specific  gravity,  1.28  to  1.30.     Yields 
60  to  68  per  cent  caked  but  very  friable  coke  and   17  to 
20  per  cent  gases.     Evaporative  factor,  7.6  to  8.3. 

Adapted  for  gas  manufacture  and  for  reverbatory  fur- 
naces. 

5.  Dry  coals,  burning  with    a  long  flame.     Color,  in- 
tense black.      Coals  hard,  break  with  conchoidal  fracture 
(splint  coal).      Specific  gravity,  1.25.     Yields  50  to  60  per 
cent  pulverulent  coke  and  20  per  cent  gas.     Evaporative 
factor,  6.7  to  7.5. 

Adapted  for  reverbatory  furnaces. 

The  ash-forming  constituents  of  coal  vary  from  0.5  to 
30  per  cent,  averaging  from  4  to  7  per  cent  in  the  best 
coals;  8  to  14  in  medium;  and  upward  of  14,  with  0.5  to 
2  per  cent  of  sulphur  in  the  worst. 

Q.  What  is  meant  by  evaporative  factor  as  employed 
by  Gruner  in  his  classification  of  coals  ? 

The  evaporative  factor,  as  employed  by  Gruner,  means 


ANTHRACITE    COAL.  13 

the  number  of  times  its  weight  of  water  is  evaporated  by 
a  unit  weight  of  coal  starting  at  100°  C.,  or  212°  F. 

Q.  What  is  anthracite  coal? 

Anthracite  is  the  most  rich  in  carbon,  greatest  in  dens- 
ity, and  hardest  of  all  varieties  of  coal.  Typical  anthracite 
coals  contain : 

Carbon 90  to  95  per  cent. 

Hydrogen i  to    3 

Oxygen  and  nitrogen i  to    3       " 

Moisture i  to    2 

Ashes 3  to    5 

The  best  varieties  of  anthracite  coal  are  slow  to  ignite., 
conduct  heat  badly,  burn  at  a  high  temperature,  radiate  an 
intense  warmth,  and  once  ignited  are  difficult  to  quench. 
Generating  almost  no  water  during  its  combustion,  anthra- 
cite coal  powerfully  desiccates  the  atmosphere  of  an  apart- 
ment in  which  it  is  burning.  Anthracite  coals  occur 
principally  in  Pennsylvania. 

J.  P.  Lesley  states  that  anthracite  is  not  an  original 
variety  of  coal,  but  a  modification  of  the  same  beds  which 
remain  bituminous  in  other  parts  of  the  region.  Anthra- 
cite beds,  therefore,  are  not  separate  deposits  in  another 
sea,  nor  coal  measures  in  another  area,  nor  interpolations 
among  bituminous  coal,  but  the  bituminous  beds  them- 
selves altered  into  a  natural  coke,  from  which  the  volatile 
bituminous  oils  and  gases  have  been  driven  off. 

Q.  What  is  the  commercial  classification  of  anthracite 
coal  ?  . 

The  larger  sizes  are  known  as  lump,  steamboat,  egg,  and 
stove  coals,  the  latter  in  two  or  three  sizes.  For  steam- 
making,  the  commerce  is  confined  almost  exclusively  to  pea 
and  smaller  sizes. 


14  COMBUSTION   OF   COAL. 

TABLE  3. — COXE  BROS.  &  Co.'s   STANDARDS   FOR  SMALL  ANTHRACITE 

COALS. 


Size. 

Made  through. 

Made  over. 

Approximate 
price  at  mines. 

Chestnut 

i-i-  inches 

|  inch 

jlto   7^ 

Pea. 

1    inch 

A      " 

I   2^ 

Buckwheat 

A     " 

* 

7e 

Rice  ... 

1      " 

a       " 

2C 

Barley  

3 

A    " 

.  IO 

The  above  meshes  are  all  round-punched. 

Q.  What  is  the  composition  of  Pennsylvania  anthracite 
coal  ? 

In  physical  appearance  anthracite  coal  differs  sufficiently 
from  other  coals  that  once  known  it  may  be  ever  after 
distinguished  at  sight.  The  fracture  presents  a  con- 
choidal  appearance  and  is  quite  homogeneous  in  structure. 

Anthracite  coal  from  Tamaqua,  Pa.,  is  compact,  slaty, 
conchoidal,  grayish  black,  splendant  (Geol.  Sur.  Pa.). 
Specific  gravity,  1.57  =  98.13  pounds  per  cubic  foot. 

Fixed  carbon 92.07  per  cent. 

Volatile  matter 5.03       " 

Ash,  white 2.90 


100.00 

Heat  units  in  one  pound  of  coa\=  14,221,  equal  to  an 
equivalent  evaporation  of  14.72  pounds  of  water  from  and 
at  212°  F.  per  pound  of  coal. 

LEHIGH  COUNTY,   PA.,  ANTHRACITE  COAL— PROXIMATE  ANALYSIS. 

Fixed  carbon 88. 15  per  cent. 

Volatile  combustible 5-28 

Moisture i.oi 

Ash 5.56       " 


100.00 


ANTHRACITE   COAL.  1 5 

Heat  units  in  one  pound  of  coal— 13,648,  equal  to  an 
equivalent  evaporation  of  14.13  pounds  of  water  from  and 
at  212°  F.  per  pound  of  coal. 

The  Buck  Mountain,  Carbon  County,  Pa.,  anthracite  coal, 
in  the  smaller  sizes,  such  as  pea  or  buckwheat,  is  largely 
employed  as  a  steam  coal.  Such  coals,  by  reason  of  the 
small  sizes,  contain  an  excess  of  slaty  matter,  which  re- 
mains on  the  grate  as  ash.  In  average  composition  they 
run  about  as  follows  : 

Carbon 82. 66  per  cent. 

Volatile  combustible 3.95        " 

Moisture 3. 04 

Ash 10.35 


IOO.OO 


Heat  units  in  one  pound  of  coal  =12, 634,  equal  to  an 
equivalent  evaporation  of  13.08  pounds  of  water  from  and 
at  212°  F.  per  pound  of  coal. 

Semi-anthracite  coal  from  Wilkesbarre,  Pa.,  in  the 
smaller  sizes,  such  as  buckwheat,  shows  an  excess  of  ash 
due  to  the  impracticability  of  picking  the  slate  out  of  the 
coal,  as  is  done  in  stove  and  larger  sizes.  The  average 
composition  of  fine  coals  from  this  locality  is  as  follows : 

Carbon 76. 94  per  cent. 

Volatile  combustible 6.42        " 

Moisture 1.34        " 

Ash   15.30 


100.00 


Heat  units  in  one  pound  of  coal  =  12,209,  equal  to  an 
equivalent  evaporation  of  12.64  pounds  of  water  from  and 
at  212°  F.  per  pound  of  coal. 


1 6  COMBUSTION   OF   COAL. 

Q.  What  is  culm  ? 

Culm  is  fine  anthracite  coal.  Formerly  this  was  waste 
product  and  had  no  commercial  value.  Culm  heaps 
abound  in  the  anthracite  regions  of  Pennsylvania,  and 
much  attention  has  been  given  to  various  processes  for  its 
employment  as  fuel.  The  late  Eckley  B.  Coxe,  an  expert 
in  all  matters  relating  to  the  subject  of  coal,  devoted  much 
time  to  the  utilization  of  culm  in  steam-making,  but  with- 
out satisfactory  commercial  results  ;  that  is,  no  demand  for 
culm  has  been  created  outside  the  mining  regions.  An- 
thracite differs  from  bituminous  or  coking  coals  in  that  it 
burns  only  at  the  surface.  Hence  it  is  absolutely  essen- 
tial to  provide  for  the  necessary  air  spaces  around  the 
pieces  on  the  grate.  This  can  be  accomplished  only  by 
careful  sizing.  With  coal  not  carefully  sized  the  inter- 
stices between  the  larger  particles  are  filled  by  the 
smaller;  and,  the  air  being  unable  to  find  a  free  enough 
passage,  combustion  is  imperfect.  Culm  banks  are  mixed 
fine  coal,  of  many  sizes,  with  a  considerable  proportion  of 
slate  and  pyrites ;  requiring  careful  attention  as  to  draft, 
firing,  and  details  of  grate,  upon  which  it  is  to  be  burned. 

Q.  What  is  semi-anthracite  coal  ? 

The  semi-anthracite  coals  are  restricted,  with  few  ex- 
ceptions, to  those  coals  which  possess  on  an  average  from 
seven  to  eight  per  cent  of  volatile  combustible  matter.  In 
consequence  of  this  combustible  matter,  part  of  which  at 
least  resides  probably  in  a  free  or  gaseous  state  in  the  cells 
of  the  coal,  this  variety  kindles  more  promptly ;  and  when 
sufficiently  supplied  with  air,  burns  more  rapidly  than  the 
hard  anthracites. 

This  coal  occurs  principally  in  Pennsylvania.     Samples 


SEMI-BITUMINOUS   COAL.  17 

from  Wilkesbarre  average  as  below :  The  semi-anthracites 
of  this  locality  are  compact,  conchoidal,  iron-black,  splend- 
ant.  Specific  gravity,  1.40  =  87.  5  pounds  per  cubic  foot. 

Fixed  carbon 88. 86  per  cent. 

Volatile  matter 7.66 

Earthy  matter 3.46       " 


The  calorific  power  of  this  coal  is  14,199  heat  units  per 
pound;  this  is  equal  to  an  equivalent  evaporation  of  14.59 
pounds  of  water  from  and  at  212°  F.  per  pound  of  coal. 

This  coal  is  held  in  high  estimation  for  domestic  use, 
and  for  the  generation  of  steam. 

Q.  What  is  semi-bituminous  coal  ? 

Semi-bituminous  coal  is  not  so  hard,  and  contains  more 
volatile  matter  than  the  anthracite  coals  proper.  In  this 
as  in  all  other  classifications  of  coals  its  limits  must  be 
fixed  somewhat  arbitrarily.  In  appearance  it  more  closely 
resembles  the  anthracite  than  the  bituminous  coals,  differ- 
ing from  anthracite  in  fracture,  as  being  less  conchoidal ; 
it  is  not  so  hard;  it  is  of  less  specific  gravity;  and  when 
thrown  upon  the  fire  it  kindles  much  more  readily  and 
burns  faster  than  anthracite. 

Cumberland,  Md.,  semi-bituminous  coal.  Specific  grav- 
ity, 1.41  =  88. 13  pounds  per  cubic  foot. 

P'ixed  carbon 68. 19  per  cent. 

Volatile  matter 17.12        " 

Sulphur 71        " 

Ash 13.98        " 


100.00 


This  coal  takes  high  rank  as  a  fuel.     Although  contain- 
ing less  carbon  than  anthracite,  it  is  quite  as  desirable  on 
2 


1 8  COMBUSTION   OF   COAL. 

account  of  the  readiness  with  which  it  kindles  and  the 
quantity  of  heat  it  is  capable  of  giving  off  when  burned  in 
steam-boiler  furnaces. 

Blossburg,  Pa.,  semi-bituminous  coal.     Specific  gravity, 
1.32  =  82.50  pounds  per  cubic  foot. 

Fixed  carbon 73. 1 1  per  cent. 

Volatile  matter 15.27       " 

Sulphur 85 

Ash 10.77       " 


100.00 


Semi-bituminous  coals  are  much  more  easily  regulated 
in  the  furnace  when  burning  than  in  the  case  of  anthra- 
cites. It  is  characteristic  of  these  coals  that  they  burn 
almost  entirely  smokeless. 

Q.  What  are  the  properties  of  bituminous  coal  ? 

Bituminous  coal  is  the  product  of  the  decomposition  of 
vegetable  matter,  and  was  formed  previously  to  or  in  the 
Cretaceous  period.  Chemically  it  occupies  a  place  between 
lignite  and  anthracite  coal,  but  the  transition  of  lignite 
into  bituminous  coal  is  as  gradual  as  the  latter  is  into  an- 
thracite, so  there  is  no  precise  line  of  demarcation  between 
these  classes  of  coal.  The  use  of  the  term  bituminous  is 
a  misleading  one,  because  none  of  the  so-called  bituminous 
coals  in  this  country  contain  any  bitumen  in  their  composi- 
tion. The  true  bitumens  are  destitute  of  organic  structure ; 
they  appear  to  have  arisen  from  coal  or  lignite  by  the  action 
of  subterranean  heat,  and  very  closely  resemble  some  of 
the  products  yielded  by  the  destructive  distillation  of  those 
bodies.  It  is  possible  that  its  name  has  been  applied  to 
certain  varieties  of  coal  on  account  of  a  similarity  between 
the  burning  of  a  coal  rich  in  hydrocarbon  and  bitumen. 


BITUMINOUS   COAL.  1 9 

The  latter  is  very  inflammable,  and  burns  with  a  red 
smoky  flame. 

All  coals  which  contain  as  much  or  more  than  18  or  20 
per  cent  of  volatile  combustible  matter  are  quite  indiscrimi- 
nately classed  among  bituminous  coals.  Some  coals  con- 
tain as  much  as  50  per  cent  of  volatile  combustible. 

In  external  properties  the  common  bituminous  coals 
range  in  color  from  a  pitch  black  to  a  dark  brown.  Their 
lustre  is  vitreous,  resinous,  or  in  the  more  fibrous  varieties 
silky;  their  structure  is  compact  and  cuboidal,  slaty, 
columnar,  and  even  fibrous ;  their  fracture,  irrespective  of 
structural  joints  and  cleavage,  is  conchoidal,  and  often 
flat  and  rectangular,  and  sometimes  fibrous. 

It  is  distinctive  of  these  coals  to  burn  with  a  more  or 
less  smoky  yellow  flame,  and  to  emit  when  burning  a  bi- 
tuminous odor. 

Q.  What  is  the  composition  of  bituminous  coal? 

In  proximate  composition — namely,  in  fixed  carbon  or 
coke,  volatile  matter  or  combustible  gases,  and  earthy 
sedimentary  residue  or  ashes — they  may  be  regarded  as 
ranging  between  the  following  general  limits: 

PROXIMATE  COMPOSITION. 

Fixed  carbon 52  to  84  per  cent. 

Volatile  matter 1 2  to  48        " 

Earthy  matter 2  to  10        " 

Sulphur i  to    3        " 

Dried  at  a  temperature  of  212°  F.,  from  i  to  5  per  cent 
of  moisture  may  be  driven  off,  with  occasionally  higher 
percentages. 

The  proportion  of  earthy  matter,  or  ash,  is  too  variable 
to  fix  a  maximum  limit,  as  all  bituminous  coals  may,  by 
impurities,  graduate  into  carbonaceous  shales. 


20 


COMBUSTION    OF   COAL. 


Bituminous  coals  may  be  regarded  as  ranging : 

ULTIMATE  COMPOSITION. 

Carbon 60  to  80  per  cent. 

Hydrogen 5  to    6  ' ' 

Nitrogen I  to    2  " 

Oxygen 4  to  10  " 

Sulphur o.  5  to    4  " 

Ash 3  to  12  " 

The  proximate  composition  of  coals  as  given  in  Table  4 
is  intended  to  give  a  general  survey  of  the  principal  bitu- 
minous coal  fields  of  the  United  States,  and  is  not  at  all 
complete  as  to  localities. 

TABLE  4. — SELECTED  AMERICAN  BITUMINOUS  COALS. 
W=  Water.      G  =  Gas.      C '=  Carbon.     A  =  Ash. 


Locality. 

Volatile 
matter. 

Coke. 

Heat 
units  per 
pound. 

Evaporation 
from 
and  at  212°. 

Alabama  .        ... 

W.     3.01 

C.    48.30 

Jefferson  Co     

G.    42.  76 

A.       5.Q3 

14  OI7 

14  51 

Arkansas  .  .          

W.     1.52 

c.  74.49 

Johnson  Co    

G.    14.73 

A.      9.26 

13,217 

13  68 

California  

W.  18.08 

C.    35.61 

Alameda  Co 

G.     "3Q.3O 

A.      7.01 

II  608 

12  OI 

Colorado 

W.     3.03 

C.    47.16 

Tremont  Co  . 

G.   42.43 

A.      6.48 

I  a  707 

14  28 

Georgia               .    .  . 

W.      1.20 

C.    60.  50 

Dade  Co  

G.    23.05 

A.    15.25 

12,553 

I2.QQ 

Illinois  

W.    8.40 

C.    54.80 

G.    31.20 

A.      5.60 

13,063 

13.52 

Vermilion  Co   .  .  . 

W.     5-73 
G.   43.70 

C.    45-37 
A.      5.15 

13,746 

14.23 

Indiana                   .  . 

W.  13.05 

C.    48.78 

Block  Coal  .  .            ... 

G.    32.34 

A.      5.83 

12,377 

12.  Si 

Cannel  Coal  
Vermilion  Co  • 

W.     3.50 
G.   48.00 

w.   5.50 

G.   44.00 

C.    42.00 
A.     6.  50 
C.   46.00 
A.     4.  50 

13,962 
13  886 

14.45 
14.37 

Indian  Territory  
Choctaw  Nation  

W.     6.66 
G.    35-42 
W.     5.16 

c.  51-32 

A.      6.60 
C.    45.88 

13,248 

13.71 

Monroe  Co  

G.    40.21 

A.      8.75 

13,247 

13.71 

BITUMINOUS   COAL. 


21 


locality. 

Volatile 
matter. 

Coke. 

Heat 

units  per 
pound. 

Evaporation 
from 
and  at  212°. 

Kansas  

W.      1.94 

C.    52.45 

Cherokee  Co 

G.    36.  77 

A.      8.84 

1-5  cg5 

I4.O6 

Kentucky 

W.     3.  60 

C.    58.80 

Muhlenberg  Co  .    .... 
Maryland  .                    ... 

G.    30.60 
W.     1.23 

A.      7.00 
C.     73.57 

13,544 

14.02 

Cumberland            .  .  . 

G.    15.47 

A.        Q.  7Q 

13  2O5 

I-I.67 

George's  Creek. 

W.       .59 
G.    18.52 

c.  74.31 

A.      6.58 

13  812 

I4.3O 

Missouri  .                

W.    0.03 

C.    46.24 

Putnam  Co     

G.    37.48 

A.      7.25 

12,852 

I3.3O 

Montana  

W.    3.01 

C.    59.71 

Cascade  Co  

G     30.23 

A.      7.05 

13,616 

I4.IO 

Nebraska 

W.      0  21 

C.    60.88 

Adams  Co  

G.    27.82 

A.    11.09 

13,390 

13.86 

New  Mexico  

W.    3.10 

C.    51.50 

Colfax  Co  
North  Carolina  
Guilford  Co  
Ohio. 

G.    35-00 
W.     1.79 
G.    29.56 
W.     8.25 

A.    10.40 
C.    58.30 
A.    10.35 
C.    53.15 

13,208 
13,302 

13.67 

-13-77 

Hocking  Valley  
Mahoning  Co 

G.    35-88 
W.     2.47 
G.    31.83 

A.      2.72 
C.    64.25 
A.      1.45 

I3,59i 
14,537 

14.07 
I5.O5 

Oregon.      ... 

W.     8.00 

C.    45.17 

Tillamook  Co  
Pennsy  1  van  ia. 

G.    37-83 
W      i  80 

A.     9  oo 

C.     5d.  Q4. 

12,754 

13.20 

Pittsburg  
Connellsville 

G.    35-34 
W.     1.93 
G.    28.71 

A.      7.92 
C.    63.26 
A.      6  10 

13,762 
13  881 

14.25 
14  37 

Youghiogheny  
Tennessee  

W.     i.  oo 
G.    35.00 
W.     3.16 

C.    58.40 
A.      5.60 
C.    54.81 

14,208 

14.71 

Marion  Co     

G.    31.04 

A.    10.09 

13,185 

13.6? 

Texas  

W.     6.67 

C.    43.54 

Palo  Pinto  
Utah 

G.    40.  20 
W.     -}  50 

A.      9.59 

C      4.3   II 

12,906 

13.36 

Iron  Co  
Virginia  
Rockingham  Co  
West  Virginia  . 

G.    43.66 
W.     1.34 
G.    30.98 
W.  *    .76 

A.      9-73 
C.    56.83 
•A.    10.85 

C.      72.  QQ 

I3,4H 
13.321 

13.88 
13-79 

Mineral  Co     .  . 

G.      IQ.  ^Q 

A.      6.86 

13,764 

14.25 

Pocahontas  (semi-bit.) 
\Vashington  . 

W.       .50 
G.    19.83 
W.     i  10 

c.  75.63 

A.      4.04 
C.     54  5O 

14,218 

14.72 

Pierce  Co  . 

G.    35.10 

A.       Q.  3O 

iV?  650 

M.I4 

\Vyoming  . 

W.    4.  20 

C.     41.  5O 

Weston  Co  . 

G.    40.  60 

A.    13.70 

12,676 

13.12 

22  COMBUSTION   OF   COAL. 

Q.  How  are  bituminous  coals  classified  ? 

Gruner's  classification  is  given  on  page  1 1,  and  in  addi- 
tion thereto  the  classification  for  economic  purposes,  by 
Percy,  is  also  given  : 

1.  Non-caking  or  free-burning  coals  rich  in  oxygen. 

2.  Caking  coals. 

3.  Non-caking  coals  rich  in  carbon. 

This  classification  of  coals  is  based  on  their  chemical 
composition,  and  therefore  on  their  calorific  powers. 

Q.  What  are  the  distinguishing  properties  of  a  caking 
coal? 

Caking  coal  is  the  name  given  to  any  coal  which,  when 
heated,  the  lumps  seem  to  fuse  together  and  swell  in  size, 
having  a  pasty  appearance  and  emitting  a  gummy  or  sticky 
substance  over  the  surface,  liberating  meanwhile  small 
streams  of  gas,  which  appear  to  escape  as  from  a  consider- 
able pressure  from  within  the  coal ;  this  escaping  gas  burn- 
ing with  a  yellow  and  sometimes  a  reddish  flame  terminat- 
ing in  smoke.  A  characteristic  of  caking  coal  is  that 
lumps,  either  large  or  small,  being  rendered  pasty  by  the 
action  of  the  heat,  will  cohere  in  the  fire  and  form  a  spongy 
looking  mass,  which  not  unfrequently  covers  almost  the 
whole  surface  of  the  grate ;  this  is  the  property  called  cak- 
ing. 

Q.  For  what  purposes  are  caking  coals  especially  de- 
sirable ? 

Caking  coals  are  employed  in  forges  where  a  hollow  fire 
is  wanted  for  heating  iron  or  steel.  Caking  coals  rich  in 
hydrocarbons  are  highly  esteemed  by  gas  manufacturers, 
because  after  driving  off  the  gas  the  remaining  coke  is  a 
valuable  by-product  which  commands  a  ready  sale.  Cak- 


COKE.  23 

ing  coals  which  will  yield  a  hard  strong  coke  are  valuable, 
inasmuch  as  coke  having  these  properties  is  greatly  in  de- 
mand in  the  manufacture  of  iron  and  steel. 

Q.  What  is  coke  ? 

Coke  is  the  solid  product  left  after  the  expulsion  of  the 
volatile  matter  from  coal  by  the  action  of  heat.  The  only 
coke  of  any  commercial  value  is  that  made  from  caking 
coals.  The  fine  coal,  screenings,  or  small  lumps  of  caking 
coals,  when  heated  sufficiently  high  and  protected  from  the 
atmospheric  air,  as  in  a  coke  oven,  gas  retort,  or  in  a  closed 
furnace,  will  have  the  volatile  portions  of  the  coal  driven 
off,  and  a  coherent  mass  of  fixed  carbon,  containing  usually 
5  to  10  per  cent  of  earthy  matter,  alone  remains;  this 
final  product  is  called  coke. 

A  very  excellent  quality  of  coke  is  made  in  the  Con- 
nellsville  region,  Pennsylvania.  It  is  there  produced  in 
enormous  quantities  for  the  manufacture  of  iron  and  steel 
in  and  near  Pittsburg,  and  for  the  remelting  of  pig  iron  in 
cupola  furnaces  in  other  localities.  The  coal  from  which 
this  coke  is  made  is  mined  in  Fayette  County,  Pa. ;  it  is 
of  columnar  structure,  inclined  to  be  granular,  and  easily 
broken  into  small  fragments.  In  appearance  this  coal 
displays  prismatic  colors  on  every  side;  its  specific  grav- 
ity is  1.28  =  80  pounds  per  cubic  foot.  By  proximate 
analysis  it  contains : 

Fixed  carbon 65.00  per  cent. 

Volatile  combustible 24.00       " 

Moisture 4. 50       " 

Ash,  white 6. 50       " 


100.00 

Coke  71.50  per  cent,  of  steel-gray  color,  having  a  me- 
tallic lustre,  columnar,  very  strong,  dense,  slightly  puffed 


24  COMBUSTION    OF   COAL. 

on  the  surface — this  coke  occurs  in  long  pieces,  not  un- 
like ordinary  cord  wood  sawed  in  half.  It  is  an  excellent 
fuel  for  melting  iron.  It  requires  a  strong  draft,  about 
the  same  as  hard  anthracite  coal.  It  yields  an  intense 
heat,  burns  free  under  a  strong  blast,  and  will  support  a 
considerable  weight  of  iron  above  it  in  the  cupola  without 
crushing. 

Q.  What  is  the  object  in  coking  coals? 

1.  The  coking  of  bituminous  coal  is  intended  to  drive  off 
the  volatile  combustible  gases  and  thereby  to  concentrate 
the  carbon  which  the  coal  contains,  so  that  the  coke  may 
be  capable  of  producing  a  higher  temperature. 

2.  To  remove  the  volatile  substances  which  on  burning, 
chiefly  for  domestic  purposes,  have  an  unpleasant  smell. 

3.  To  deprive  the  coal  of   the  property  of  becoming 
pasty  at  a  high  temperature,   in  iron  blast  furnaces  for 
instance,  in  consequence  of  which  the  blast  cannot  pene- 
trate sufficiently,  and  the  process  of  the  furnace  becomes 
disordered. 

4.  To  remove  part  of  the  sulphur,  which  coal  frequently 
contains  in  the  form  of  sulphide  of  iron. 

The  production  of  good  coke  requires  a  combination  of 
qualities  not  very  frequently  met  with  in  coal,  and  hence 
first-rate  coking  coals  can  be  procured  only  from  certain 
districts. 

Q.  What  are  the  general  properties  of  coke  ? 

The  properties  of  coke  must  in  some  degree  be  influ- 
enced by  the  properties  of  the  coal  from  which  it  is  made. 
In  external  features  it  will  depend  whether  the  coke  is  the 
product  of  a  gas  retort  or  that  of  an  oven,  the  general  ap- 
pearance being  wholly  unlike.  As  an  article  of  commerce 
cokes  contain :  Carbon,  80  to  96  per  cent ;  ash,  2  to  15; 


CANNEL   COAL.  2$ 

hygroscopic  moisture,  i  to  5  ;  and  is  capable  of  absorbing 
from  5  to  10  per  cent  additional  water  if  exposed  to  the 
weather. 

Coke  weighs  40  to  60  pounds  per  cubic  foot  and  the 
denser  varieties  more.  About  60  cubic  feet  of  space  are 
required  for  storage  per  ton. 

Q.  What  properties  in  the  coal  are  required  for  making 
the  best  coke  ? 

To  make  a  homogeneous  good  coke  the  fixed  carbon  of 
the  coal  must  be  of  a  kind  that  will  melt  at  the  lowest  pos- 
sible temperature;  for  if  the  process  of  coking  produces 
the  least  pressure  on  the  volatile  hydrocarbons  whereby 
there  is  an  increase  of  heat,  such  pressure  causes  so  com- 
plete a  liquefaction  and  expansion  of  the  fixed  carbon  that 
the  coke  is  left  cellular  instead  of  being  compact. 

Q.  For  what  purposes  is  coke  chiefly  employed  ? 

Coke  may  be  employed  in  all  kinds  of  firing  which  do 
not  require  a  large  flame,  but  it  is  most  effective  in  those 
instances  in  which  great  heat  is  required  in  a  small  space, 
as,  for  instance,  in  crucible  meltings,  in  smelting  of  iron 
ores  in  blast  furnaces,  in  remelting  of  pig  iron  in  cupola 
furnaces,  etc.  When  a  sufficient  quantity  of  air  is  ad- 
mitted, coke  produces  a  far  greater  heat  than  charcoal. 
As  it  remains  longer  in  the  furnace  than  charcoal  before 
being  ignited,  it  undergoes  a  better  preparatory  heating 
before  ignition,  and  by  this  means  its  effect  is  increased. 

Q.  What  is  cannel  coal  ? 

Cannel  coal  is  a  variety  of  bituminous  coal  very  rich  in 
hydrogen.  In  appearance  this  coal  differs  from  all  other 
bituminous  coals.  Its  structure  is  more  nearly  homoge- 
neous than  others,  being  a  compact  mass,  varying  from 


26  COMBUSTION    OF   COAL. 

brown  to  black  in  color,  and  having  usually  a  dull  resinous 
lustre.  When  broken  it  does  not  usually  preserve  any 
distinct  order  of  fracture,  and  is  liable  to  split  in  any 
direction.  On  account  of  its  being  excessively  rich  in 
hydrocarbons  it  is  highly  esteemed  as  a  gas  coal,  prefer- 
ence being  given  to  those  coals  in  which  hydrogen  bears 
the  greatest  proportion  to  the  contained  oxygen. 

The  amount  of  combustible  matter  which  it  contains, 
and  the  readiness  with  which  this  is  given  off  in  com- 
bustion, account  for  the  name  given  it  by  the  miners 
as  "  cannel,"  a  corruption  of  candle  coal.  This  coal 
kindles  readily  and  burns  without  melting,  emitting  a 
bright  flame  like  that  of  a  candle.  When  thrown  in  the 
fire  the  piece  splits  up  into  fragments,  producing  a  crack- 
ling noise,  which,  from  a  fancied  resemblance,  has  also 
received  the  name  of  "  parrot "  coal.  It  is  highly  es- 
teemed for  domestic  use,  being  especially  bright  and 
cheerful  when  burned  in  an  open  grate.  Cannel  coals  are 
used  for  enriching  gas  made  from  coals  containing  a  large 
amount  of  volatile  combustible,  but  somewhat  deficient  in 
illuminating  power. 

Q.  What  is  the  composition  of  cannel  coal  ? 

Cannel  coal  occurs  in  so  few  localities  that  the  variations 
in  composition  are  less  noticeable  than  is  the  case  with 
other  varieties  of  bituminous  coal.  Cannel  coal  from 
Breckenridge,  Ky.,  analyzed  by  Dr.  Peters,  resulted  in : 

PROXIMATE  ANALYSIS. 

Carbon 32.00  per  cent. 

Volatile  combustible 54.40 

Moisture 1.30       " 

Ash 12.30       " 


CANNEL   COAL.  27 

ELEMENTARY  ANALYSIS. 

Carbon 68. 128  per  cent. 

Hydrogen     6. 489 

Nitrogen 2.274 

Oxygen  and  loss 5. 833 

Sulphur 2. 476 

Ash '. 14. 800 

100. ooo 

Cannel  coal  from  Davis  County,  Ind.  Analysis  by  E. 
T.  Cox.  Specific  gravity,  1.229  =  76.81  pounds  per  cubic 
foot. 

PROXIMATE  ANALYSIS. 

Carbon 42.00  per  cent. 

Volatile  combustible 48.  50 

Moisture 3.50 

Ash,   white 6.00       " 


100.00 
Coke,  48  per  cent,  laminated,  not  swollen,  lustreless. 

ELEMENTARY  ANALYSIS. 

Carbon 71. 10  per  cent. 

Hydrogen 6. 06 

Oxygen 12.74 

Nitrogen 1. 45 

Sulphur i.oo 

Ash... 7.65 

100.00       " 

Q.  What  is  the  calorific  value  of  cannel  coal  ? 

The  calorific  power  of  cannel  coal  from  Davis  County, 
Ind.,  analysis  of  which  is  given  on  this  page,  is  1 3, 1 3 1  heat 
units  per  pound  of  coal.  This  is  equal  to  an  equivalent 
evaporation  of  13.58  pounds  of  water  from  and  at  212°  F. 
per  pound  of  coal. 


28  COMBUSTION   OF   COAL. 

Q.  What  properties  do  non-caking  coals  exhibit  in  the 
fire? 

Non-caking  coals  have  the  property  of  burning  free  in 
the  fire  much  the  same  as  wood  charcoal  burns;  that  is, 
heat  does  not  cause  them  to  fuse  or  run  together  in  the 
fire.  Perhaps  the  representative  non-caking  bituminous 
coal  is  the  block  coal  of  the  Western  States,  and  notice- 
ably that  of  Indiana. 

Q.  What  is  block  coal  ? 

Block  coal  is  a  non-caking  bituminous  coal  occurring  in 
large  quantities  in  Indiana.  It  may  be  described  as  lami- 
nated in  structure,  consisting  of  successive  layers  of  coal, 
easily  separated  into  thin  horizontal  slices,  not  unlike 
slate.  Between  these  slices  of  coal  is  a  layer  of  fibrous 
carbon  resembling  charcoal.  In  appearance  it  has  a  dull, 
lustreless  face  on  the  line  of  separation,  and  glistening  or 
resinous  black  when  broken  at  right  angles  to  its  horizon- 
tal face.  A  peculiarity  of  this  formation,  and  that  which 
gives  it  its  name,  is  the  presence  of  fractures  occurring 
in  the  coal  bed  at  right  angles,  or  nearly  so,  and  extending 
from  top  to  bottom  of  the  seam,  enabling  the  miner  to  get 
it  out  in  rectangular  blocks,  as  these  lines  of  fracture  indi- 
cate or  permit.  It  is  a  very  strong  coal,  and  will  burn 
well  under  a  heavy  load  without  crushing.  The  blocks 
are  very  compact,  and  will  endure  rough  handling  and 
stocking  without  suffering  material  loss  from  abrasion. 

A  sample  of  typical  block  coal  from  near  Brazil,  Clay 
County,  Ind.,  has  the  following  characteristics :  The  coal 
of  a  dull  lustreless  black,  in  thin  laminae,  separated  by 
fibrous  charcoal  partings,  very  strong  across  the  bedding 
lines,  free  from  pyrites  and  calcite.  A  sample  fresh 


BLOCK   COAL.  29 

from  the  mine,  and  holding  an  excess  of  moisture,  analysis 
by  E.  T.  Cox.  Specific  gravity,  1.285  =  80.31  pounds  per 
cubic  foot. 

Fixed  carbon 56. 50  per  cent. 

Volatile  combustible 32. 50 

Moisture 8. 50 

Ash,  white 2. 50 

100.00       " 
Coke  =  59  per  cent,  laminated,  not  swollen,  lustreless. 

The  8.50  per  cent  of  moisture  was  reduced  by  exposure 
to  the  air  to  about  3.  50  per  cent.  The  heat  units  in  the 
wet  coal  =13, 5 88,  and  that  of  the  dry  coal  =  14,400. 

This  coal  is  used  as  fuel  in  blast  furnaces  for  smelting 
iron,  and  in  puddling  furnaces.  It  is  largely  used  for 
steam- making  and  for  domestic  stoves,  grates,  etc. 

A  test  of  Indiana  block  coal  by  A.  F.  Nagle  in  steam- 
making  yielded  as  follows : 

Ratio  of  heating  to  grate  surface                           =  50  to  I 

Ash,  per  cent                                                            —  7-25 
Rate  of  combustion,  pounds  per  square  foot  of 

grate  15 

Temperature  of  escaping  gases                               =  557°  F« 
Evaporation  per  pound  of  combustible  from  and 

at  212°                                                                =  10.05  pounds. 

Q.  What  is  brown  coal  ? 

Brown  coal  is  an  imperfect  coal.  The  term  is  often 
used  interchangeably  with  lignite.  The  brown  coal  of  the 
Germans  is  distinguished  from  true  coals  by  the  large  pro- 
portion of  oxygen  in  its  composition.  The  chemical  dif- 
ference between  brown  coal  and  lignite  may  be  determined 
by  dry  distillation,  in  which  the  lignite  yields  acetic  acid 
and  acetate  of  ammonia,  whereas  the  brown  coal  produces 
only  ammoniacal  liquor.  Woody  fibre  gives  rise  to  acetic 


30  COMBUSTION   OF   COAL. 

acid.  Lignite  must  therefore  still  contain  undecomposed 
woody  fibre.  It,  together  with  brown  coal,  belongs  chiefly 
to  the  Cretaceous  and  Tertiary  periods  (Cox).  According 
to  their  geological  age  brown  coals  have  either  a  distinct 
texture  (true  lignite,  fibrous  brown  coal),  or  are  without 
organic  structure  and  earthy  in  fracture  (earthy  brown 
coal),  or  black,  shining,  with  conchoidal  fracture. 

Thorpe's  analysis  of  organic  substance  consists  of :  Car- 
bon, 60;  hydrogen,  5  ;  oxygen,  35  =  100  in  fibrous  brown 
coal;  and  carbon,  75;  hydrogen,  5;  oxygen,  20  =  100  in 
conchoidal  brown  coal. 

The  analysis  of  brown  coal  from  Ballard  County,  Ky., 
shows  it  to  contain  20  to  30  per  cent  less  fixed  carbon 
than  coals  of  the  Carboniferous  epoch,  and  a  larger  quan- 
tity of  hygrometric  moisture.  The  specific  gravity  of  this 
coal  is  1.173. 

Fixed  carbon 31.0  per  cent. 

Volatile  combustible 48.0       " 

Moisture 11.5        " 

Ash,  white 9.5       " 


100. o 


The  large  quantity  of  hygrometric  moisture  in  this  coal 
lessens  its  evaporative  power  as  compared  with  any  aver- 
age bituminous  coal  for  steam-making.  It  is  quite  im- 
probable that  any  considerable  quantity  of  available  heat  is 
given  off  by  the  volatile  combustible  in  this  coal ;  and  that 
its  heating  power  is  limited,  almost  if  not  entirely,  to  the 
fixed  carbon,  yielding  4,495  heat  units,  or  an  equivalent 
evaporation  of  4.66  pounds  of  water  from  and  at  212°  F. 
per  pound  of  coal. 

Q.  What  is  lignite? 

Lignite  is  classed  among  mineral  coals,  and  includes 


LIGNITE.  3 1 

those  varieties  which  form  the  intermediate  stage  between 
peat  and  true  coals  of  the  Carboniferous  age.  It  is  believed 
to  be  of  later  origin  than  bituminous  coal,  and  is  in  a  less 
advanced  stage  of  decomposition.  The  woody  fibre  and 
vegetable  texture  of  lignite  are  almost  entirely  wanting  in 
coal,  though  there  is  little  doubt  that  they  are  of  one  com- 
mon origin. 

Lignite  varies  considerably  in  appearance  and  structure, 
usually,  however,  preserving  a  wood-like  appearance  when 
broken.  The  fracture  is  uneven,  presenting  a  brown  to  a 
very  dark  brown-black  color,  with  a  dull  and  frequently  a 
fatty  lustre.  Lignites  break  easily  and  crumble  in  han- 
dling ;  they  will  not  bear  rough  transportation  to  great  dis- 
tance ;  neither  will  they  bear  long-continued  exposure  to 
weather,  crumbling  rapidly.  As  a  fuel  lignite  must  be  used 
in  its  natural  state,  and  near  where  it  is  mined,  to  get  the 
best  results.  It  is  non-coking  in  the  fire,  and  yields  but 
moderate  heat  as  compared  with  the  best  bituminous 
coals. 

In  specific  gravity  lignites  vary  from  1. 10  to  1.35,  cor- 
responding to  68.75  to  84.38  pounds  per  cubic  foot. 

Q.  Where  are  lignites  principally  found? 

Lignites  and  "  brown  coal  "  occur  plentifully  on  the 
continent  of  Europe.  In  the  United  States  very  extensive 
deposits  occur  in  Colorado,  Nevada,  Utah,  Wyoming,  New 
Mexico,  California,  Oregon,  and  Alaska,  and  in  lesser 
quantity  in  some  other  States.  As  the  States  and  Terri- 
tories west  of  the  Mississippi  are  developed,  lignite  will 
become  a  matter  of  growing  importance,  as  it  must  be- 
come their  chief  fuel  after  the  disappearance  of  the  for- 
ests. 


32  COMBUSTION   OF  COAL. 

Q.  What  is  the  composition  of  lignite? 

The  lignites  of  the  United  States  vary  greatly  in  their 
chemical  composition,  consisting  of : 

Fixed  carbon 40  to  70  per  cent. 

Volatile  combustible 23  to  48       " 

Moisture 4  to  40       " 

Ash 3  to  20       " 

Colorado  lignite,  Canon  City:  Color,  jet  black;  specific 
gravity,  1.279. 

Fixed  carbon 56. 80  per  cent. 

Volatile  combustible 34. 20       ' ' 

Moisture 4.  50       " 

Ash,  ochre  yellow 4. 50      " 

100.00       " 
Coke  =  61.30  percent,  slightly  swollen,  unchanged,  semi-lustrous  (Cox). 

Washington  lignite,  Billingham  Bay :  Color,  glossy 
black ;  fracture  slaty  and  parallel  to  stratification.  In  the 
opposite  direction  the  fracture  is  irregular  and  brittle. 

PROXIMATE  ANALYSIS. 

Fixed  carbon 58. 25  per  cent. 

Volatile  combustible 31-75       " 

Moisture 7.00       " 

Ash,  reddish  brown 3.00       " 


100.00 
Coke  =  61.25  per  cent,  slightly  shrunken,  dull  black. 

ULTIMATE  ANALYSIS. 

First  Second 

sample.  sample. 

Carbon Per  cent  68. 454  67.090 

Hydrogen "           6.666  4.555 

Sulphur "           i.  ooo  i. ooo 

Water  at  212°  F "           7.000  7.000 

Ashes "           3.400  3-100 

Oxygen,  nitrogen  and  loss. ,  ., "         13.480  17.255 

100.000  100.000 


LIGNITE,  33 

Samples  contained  a  large  amount  of  oxygen  and  were 
deficient  in  the  amount  of  hydrocarbons,  and  therefore 
more  difficult  of  ignition  than  most  of  the  Western  varie- 
ties of  bituminous  coals;  but  it  is  rich  in  fixed  carbon  in 
the  coke  and  will  therefore  be  durable.  It  is  intermediate 
in  composition  of  its  ultimate  elements  to  cannel  coal  and 
lignites  (Cox). 

Kentucky  lignite,  Ballard  County :  Sample  had  much 
the  appearance  of  coal,  hence  apt  to  be  mistaken  for  it ; 
but  it  is  of  much  more  recent  origin.  Specific  gravity, 

1. 201. 

Fixed  carbon 40  per  cent. 

Volatile  combustible 23       ' ' 

Moisture 30       " 

Ash,  reddish  yellow 7 

100       " 

Coke  =  47  per  cent.     Reduced  in  bulk  and  nearly  the  same  shape  as  orig- 
inal specimen  (Cox) . 

Arkansas  lignite,  Ouachita  County :  This  lignite  has  a 
rhomboidal  cleavage.  Can  be  cut  with  a  knife,  and  re- 
ceives a  good  polish,  which  gives  it  a  much  blacker  ap- 
pearance. It  is  solid,  heavy,  compact,  of  a  bluish-brown 
color,  disintegrating,  however,  by  exposure  to  the  atmos- 
phere. 

Fixed  carbon 34.  50  per  cent. 

Volatile  combustible 28.  50       " 

Moisture  at  260°  F 32.  oo       " 

Ash 5.00       " 


100.00 
Coke  =  39, 5  per  cent. 

Vancouver's  Island  lignite :  Color,  dull  black,  submetal- 
lic.  Fracture,  foliated  and  slaty,  numerous  partings  filled 
with  scales  of  carbonate  of  lime. 


34  COMBUSTION   OF   COAL. 

Fixed  carbon  62  per  cent. 

Volatile  combustible 31        " 

Moisture 4       " 

Ash,  reddish  brown 3 


Coke  =  65  per  cent.     This  lignite  shrinks  slightly  in  coking,  and  is  dull 
black  in  color  (Cox). 

Texas  lignite,  Robertson  County:  Sample  taken  from 
seam  ten  feet  thick.  Color,  lustreless,  dull  brown,  with 
irregular  fracture  and  much  inclined  to  shrink,  crack,  and 
fall  to  pieces  on  exposure  to  air.  Specific  gravity,  1.232. 

Fixed  carbon 45.  oo  per  cent. 

Volatile  combustible 39. 50        " 

Moisture 11.00 

Ash,  white 4. 50        " 


100.00 


Coke,    slightly  shrunken,   lustreless,   and  bears  a  close   resemblance    to 
wood  charcoal.      Heat  units,  13,068. 

The  ash  of  lignites  is  extremely  variable  as  to  quality 
as  well  as  to  quantity.  In  composition  it  is  similar  to 
that  of  bituminous  coal.  It  differs  from  the  ash  of  peat 
in  the  low  percentage  of  phosphoric  acid.  Usually  it  is 
rich  in  sulphur,  as  gypsum,  iron  pyrites,  and  sometimes  as 
free  sulphur. 

Q.  What  is  the  quality  of  coke  obtained  from  lignite  ? 

Lignites  are  in  general  non-caking  in  an  open  fire.  The 
coke  obtained  by  distillation  from  the  best  lignites  is  not 
of  good  quality  and  takes  rank  much  below  the  inferior 
grades  of  coke  made  from  gas  coals. 

Q.  How  are  woods  classified? 

Wood  as  a  fuel  is  commonly  divided  into  two  classes — 
hard  and  soft.  Hard  woods  include  the  heavy  compact 


WOOD. 


35 


varieties,  such  as  oak,  hickory,  beech,  elm,  ash,  walnut,  etc. 
The  soft  woods  include  pine,  birch,  poplar,  willow,  etc. 

The  specific  gravity  of  wood  varies  considerably.  Air- 
dried  woods,  with  20  per  cent  hygroscopic  moisture,  hav- 
ing a  specific  gravity  of  more  than  0.55  are  classed  as  hard 
woods ;  with  a  lower  specific  gravity  they  are  classed  as 
soft  woods.  After  complete  expulsion  of  air  from  the 
pores  the  specific  gravity  is  the  same  in  all  woods,  viz.,  1.5. 

Q.  What  is  the  composition  of  wood? 

Wood  consists  of  about  96  per  cent  of  organic  tissue 
and  4  per  cent  of  sap,  containing  a  small  proportion  of 
inorganic  matter.  Freshly  cut  green  wood  contains  on  an 
average  about  45  per  cent  of  moisture;  and  after  long 
exposure  to  the  atmosphere  under  favorable  conditions  it 
still  retains  from  1 8  to  20  per  cent  of  moisture,  a  matter 
of  practical  importance  in  the  direct  application  of  wood 
as  fuel.  The  accompanying  table,  by  M.  Eugene  Chevan- 
dier,  shows  the  composition  of  several  well-known  varie- 
ties of  wood : 

TABLE  5. — COMPOSITION  OF  WOOD   (Chevandier) . 


Woods. 

COMPOSITION  IN  PER  CENT. 

Carbon. 

Hydrogen. 

Oxygen. 

Nitrogen. 

Ash. 

Beech    

49-36 
49.64 
50.20 
49-37 
49-90 

6.01 
5-92 
6.20 
6.21 

5.96 

42.69 
41.16 
41.62 
41.60 
39-56 

0.91 
1.29 

I.I5 
.96 

.96 

I.OO 
1.97 

.81 

1.86 
3-37 

Oak  

Birch  

Poplar  
Willow  

Average  .... 

49.70 

6.06 

41.30 

1.05 

i.  80 

Q.  What  quantity  of  moisture  is  contained  in  wood  ? 
Wood  contains  about  45   per   cent  of   moisture  when 
freshly  cut.     Some  of  this  is  lost  by  subsequent  evapora- 


COMBUSTION   OF  COAL. 


tion  in  the  atmosphere,  but  there  still  remains  about  20 
per  cent  of  moisture  which  cannot  be  expelled  except  by 
means  of  artificial  heat.  The  following  table,  prepared  by 
M.  Violette,  shows  the  proportion  of  water  expelled  from 
wood  at  gradually  increasing  temperatures.  The  samples 
of  wood  operated  upon  had  been  kept  in  store  during  two 
years.  In  each  experiment  the  specimens  were  exposed 
during  two  hours  to  desiccation  in  a  current  of  superheated 
steam,  of  which  the  temperature  was  gradually  raised  from 
257°  to  437°  F.  When  wood,  which  has  been  strongly 
dried  by  means  of  artificial  heat,  is  left  exposed  to  the  at- 
mosphere, it  reabsorbs  about  as  much  water  as  it  contains 
in  its  air-dried  state. 

TABLE  6. — WATER  EXPELLED  FROM  100  PARTS  OF  WOOD  (Violette). 


Temperatures. 

Oak. 

Ash. 

Elm. 

Walnut. 

2C7°  F 

m  26 

14  78 

15-3,2 

je.  55 

102°  F 

i7.cn 

16  19 

17  O2 

17  43 

•74.7°  F              ... 

32.  13 

21.22 

36.04? 

21  OO 

102°  F  . 

35.80 

27.51 

-1-1.38 

41.77  ? 

437°  F..                

44.  -Ji 

33.38 

40.56 

36.56 

Q.  What  is  a  distinguishing  property  of  wood  as  a 
fuel? 

Though  the  calorific  intensity  of  wood  is  small  as  com- 
pared with  coal,  its  combustibility  is  greater  than  that  of 
any  other  solid  fuel,  and  it  gives  more  flame. 

Q.  What  is  bagasse? 

Bagasse  is  the  woody  fibre  of  sugar-cane  after  the 
saccharine  juices  have  been  expelled  for  sugar-making. 
Special  furnaces  have  been  contrived  for  burning  it,  and 
with  fair  results.  The  contained  water  is  about  50  per 
cent  of  the  gross  weight.  The  remaining  fibre  is  not  un- 


TAN.  37 

like  wood  in  its  heat-giving  power.  On  an  average  six 
pounds  of  bagasse  are  equivalent  to  one  pound  good  bitu- 
minous coal. 

Q.  What  is  tan  ? 

Tan  is  the  spent  bark  from  which  the  tannic  acid  has 
been  extracted  in  the  process  of  tanning  leather.  The 
barks  commonly  used  are  oak  and  hemlock.  The  princi- 
pal drawback  to  tan  as  a  fuel  is  its  contained  moisture, 
and  for  this  reason  special  furnaces  are  made  for  burning 
it.  Tan  bark,  as  commonly  used  for  fuel,  will  yield  about 
3,600  heat  units  per  pound,  which  is  one-half  the  value  of 
ordinary  dry  wood,  and  about  one-fourth  the  value  of  good 
bituminous  coal. 

If  it  were  not  for  the  contained  moisture  in  tan  very 
much  higher  calorific  results  could  be  obtained.  Accord- 
ing to  M.  Peclet  5  parts  of  oak  bark  produce  4  parts  of 
dry  tan,  and  the  heating  power  of  perfectly  dry  tan,  con- 
taining 15  per  cent  of  ash,  is  6,100  heat  units,  while  that 
of  tan  in  an  ordinary  state  of  dryness,  containing  30  per 
cent  of  water,  is  only  4,284  heat  units.  The  equivalent 
evaporation  from  and  at  212°  F.  would  be : 

Perfectly  dry  tan,  '        =6.31  pounds  of  water. 

Wet  tan,  30  per  cent  water,  -    —  =  4.44  pounds  of  water. 

Results  which  are  much  higher  than  obtain  in  average 
practice. 

Q.  What  is  peat? 

Peat  is  the  product  of  the  decay  of  plants  which  are  un- 
dergoing a  gradual  transformation  by  a  process  of  slow 
burning  or  carbonization,  in  which  the  oxygen  of  the 


38  COMBUSTION   OF   COAL. 

plants  is  .being  liberated  under  special  conditions  of  air 
and  moisture,  leaving  a  spongy,  carbonaceous  mass,  in 
which  the  remains  of  the  plants  are  often  so  well  preserved 
that  species  may  easily  be  distinguished. 

In  color  peat  varies  from  a  yellowish  brown  through  all 
gradations  to  a  very  dark  brown,  almost  black.  The  struc- 
ture of  the  former  is  light,  spongy,  and  fibrous;  the  latter 
is  more  compact  and  pitchy  in  appearance,  the  fibrous  tex- 
ture being  almost  entirely  obliterated.  In  advanced  stages 
of  decomposition  it  is  compact  and  dense,  presenting  an 
earthy  fracture  when  broken  ;  in  general  the  darker  the 
peat  the  richer  it  is  in  carbon. 

Q.  What  is  the  composition  of  peat? 

In  its  natural  and  more  advanced  state  peat  contains 
about  75  per  cent  of  its  entire  weight  of  water.  In  the 
earlier  stages  of  decomposition  the  quantity  of  water  more 
nearly  approaches  90  per  cent,  the  peat  being  of  the  con- 
sistency of  mire,  and  is  of  course  totally  unfit  for  any  of 
the  purposes  for  which  fuel  is  employed. 

Peat  shrinks  very  much  in  drying,  yet  20  to  30  per 
cent  of  moisture  still  remain  in  ordinary  air-dried  samples. 
The  remaining  product  is  decomposed  vegetable  matter 
and  contains  the  elements  common  to  plants.  The  chemi- 
cal composition  of  peat  varies  according  to  its  stage  of 
decomposition.  The  following  analysis  of  Irish  peat  is 
upon  the  authority  of  Sir  Robert  Kane  : 


Light  fibrous. 

and  dense. 

Carbon  ...................................   58-53  56-34 

Hydrogen  ................................     5-73  4-  81 

Oxygen  ...................................   32.  32  3°-  20 

Nitrogen  ...................................  93  -74 

Ash  ......................................     2.47  7-90 


PEAT.  39 

These  samples  yielded  by  distillation : 

Light  fibrous.       C°m/act 
and  dense. 

Water 38.1  38.1 

Crude  tar 4-4  2.8 

Charcoal 21.8  32.6 

Gas 35-7  26. 5 

The  tar  when  redistilled  yielded  water,  paraffine  oils,  char- 
coal, and  gas.  The  water  yielded  chloride  of  ammonium, 
acetic  acid,  and  wood  spirit. 

The  inorganic  constituents  of  peat  vary  from  0.5  to  20, 
or  even  50  per  cent,  according  to  the  elevation  at  which 
the  peat  was  formed.  The  average  ash-giving  constitu- 
ent is  from  6  to  12  per  cent,  and,  unlike  that  of  wood, 
the  ash  is  poor  in  alkalies,  and  consists  chiefly  of  a  mix- 
ture of : 

Argillaceous  sand up  to  35  per  cent. 

Magnesia-bearing  gypsum , '       40 

Ferric  oxide "     30       " 

Alkalies "       3 

With  traces  of  phosphoric  acid  and  chlorine. 

Q.  What  is  the  density  of  peat? 

The  density  of  peat  varies  according  to  its  occurrence 
with  reference  to  the  surface  of  the  ground,  that  belong- 
ing to  the  upper  stratum  being  lightest.  The  specific  grav- 
ity of  the  light  fibrous  peat  in  the  preceding  question  is  but 
0.280,  while  the  compact  and  dense  peat  in  the  same  para- 
graph is  0.65  5.  Thus  the  light  fibrous  peat  =  1 7.  5  pounds 
per  cubic  foot,  or  114  cubic  feet  per  ton  of  2,000  pounds. 
The  compact  and  dense  peat  =  40.94  pounds  per  cubic  foot, 
or  48.85  cubic  feet  per  ton  of  2,000  pounds.  Compressed 
peat  will  weigh  from  70  to  85  pounds  per  cubic  foot,  or 
from  24  to  30  cubic  feet  per  ton  of  2,000  pounds.  The 
dense  peat  found  in  the  lower  strata  of  peat  beds,  and 


40  COMBUSTION   OF   COAL. 

which  is  in  a  more  advanced  state  of  decomposition,  is  not 
easily  compressible.  Its  specific  gravity  is  seldom  greater 
than  that  of  water  or  unity ;  therefore  the  densest  varie- 
ties will  seldom  weigh  more  than  62.5  pounds  per  cubic 
foot,  or  32  cubic  feet  per  ton. 

Q.  How  is  peat  prepared  for  use  as  fuel? 

The  machinery  used  for  making  peat  fuel  is  not  expen- 
sive, and  requires  but  little  attention  when  in  operation. 
If  the  fibre  of  the  upper  formation  of  peat  is  crushed  or 
milled  while  it  is  still  wet,  the  contraction  in  drying  is, 
much  increased ;  and  as  surface  peat  is  always  fibrous  and 
spongy,  it  is  the  lightest.  This  breaking  up  of  its  fibres 
facilitates  its  subsequent  compression  for  use  as  fuel,  the 
degree  of  compression  varying  with  the  density  of  the 
peat,  which  grows  more  dense  in  the  lower  strata,  where 
the  fibrous  texture  is  nearly  or  wholly  obliterated. 

In  Canada  the  peat  is  cut  and  air-dried,  after  which  it  is 
pulverized  by  being  passed  through  a  picker  and  auto- 
matically deposited  in  a  hopper,  which  feeds  a  steel  tube 
about  two  inches  in  diameter  and  fifteen  inches  long. 

The  pulverized  peat  is  forced  through  this  tube  by  press- 
ure, and  formed  into  cylindrical  blocks  three  inches  in 
length  and  almost  equal  in  density  to  anthracite  coal. 
The  fuel  is  non-friable  and  weather-proof  by  reason  of  its 
solidity  and  the  glaze  imparted  to  it  by  frictional  contact 
with  forming  dies.  The  inherent  moisture  of  the  peat  is 
reduced  to  12  per  cent  of  the  mass.  It  is  claimed  that; 
peat  can  be  thus  prepared  at  a  cost  of  60  cents  per  ton. 

Q.  What  are  the  properties  of  peat  charcoal  ? 

The  charcoal  produced  by  the  carbonization  of  ordinary 
air-dried  peat  is  very  friable  and  porous;  it  takes  fire 


PEAT.  41 

readily,  and  when  ignited  continues  to  burn  until  its  car- 
bonaceous matter  is  wholly  consumed;  it  scintillates  in  a 
remarkable  degree  when  burnt  in  a  smith's  fire;  its  ex- 
tinction when  in  mass  is  difficult,  and  hence  this  is  the 
troublesome  part  of  its  manufacture  by  the  usual  method 
of  carbonization  in  piles ;  and  it  is  so  little  coherent  that 
it  cannot  be  conveyed  without  much  of  it  being  crushed  to 
dust. 

When  sufficiently  coherent,  and  when  the  percentage  of 
phosphoric  acid  is  low,  it  may  be  used  in  low,  small  fur- 
naces. Peat  charcoal  is  easily  kindled,  and  has  a  calorific 
power  of  11,700  to  12,600  heat  units.  It  is  not  adapted 
for  iron-making,  but  may  advantageously  be  used  for  gas 
furnaces  on  account  of  the  large  size  of  the  lumps,  absence 
of  clinkers,  and  the  fact  that  the  ash  readily  falls  through 
the  bars. 

Q.  Where  is  peat  principally  found  ? 

Peat  formations  are  confined  to  cold  and  temperate 
countries  and  swampy  ground.  It  occurs  in  the  United 
States,  Canada,  Ireland,  Sweden,  Germany,  France,  and 
other  countries.  In  Europe  peat  is  used  not  only  for  do- 
mestic purposes,  but  for  metallurgical  purposes  as  well. 
One  of  the  most  extensive  peat  beds  known  is  in  the  Kan- 
kakee  valley,  Indiana,  the  bed  being  some  three  miles  wide 
and  sixty  miles  long,  varying  from  five  to  fifty  feet  in 
thickness. 

Q.  How  may  peat  be  classified? 

Peat  may  be  classified :  (i)  according  to  the  localities 
where  it  has  been  formed,  as  lowland  and  mountain  peat; 
(2)  according  to  its  age,  as  recent  peat  with  distinct  vege- 
table structure,  and  old  peat  of  a  dark  brown  or  black 
color,  with  more  traces  of  organic  texture ;  (3)  according  to 


42  COMBUSTION   OF   COAL. 

the  mode  in  which  it  has  been  extracted,  as  cut  peat  or 
dredge  peat  (Thorpe). 

Q.  What  are  fuel  briquettes  ? 

Briquette  is  a  name  given  to  a  small  body  of  prepared 
fuel,  made  up  chiefly  of  the  culm  of  bituminous  coal  held 
together  by  a  bonding  material,  also  combustible,  the  mix- 
ture being  then  compressed  into  a  compact  mass,  of  a  size 
and  shape  suitable  for  use  as  fuel. 

Briquette-making  has  become  quite  an  industry  in  Ger- 
many, Austria,  and  France,  where  the  fuel  question  is 
much  more  important  than  ii  is  with  us.  The  culm  piles 
are  being  utilized  in  those  countries  and  made  a  profitable 
source  of  income. 

Brown  coal  has  so  far  been  the  chief  material  for  bri- 
quettes. Some  recent  experiments  with  briquettes  made 
of  solidified  petroleum  or  residuum  have  been  made,  which, 
however,  did  not  result  satisfactorily,  for  the  reason  that 
the  boilers  were  unable  to  withstand  the  intense  heat  de- 
veloped by  this  kind  of  fuel. 

L Industrie  describes  a  process  devised  by  the  chemist 
Velna,  who  uses  petroleum  or  mineral  tar  only  for  enrich- 
ing culm  and  other  inferior,  formerly  worthless  combus- 
tibles, and  produces  briquettes  from  this  material  the 
heating  power  of  which  is  30  per  cent  higher  than  that  of 
good  coal.  He  first  prepares  a  mixture  consisting  of  pe- 
troleum or  bituminous  shale  tar,  oleine  and  soda  in  suit- 
able proportion,  and  by  this  means  the  culm,  slack,  or  coal 
dust  is  cemented  together.  Three  kinds  of  briquettes  are 
produced  in  this  way,  namely,  industrial  briquettes  for 
general  firing  purposes,  gas  briquettes  for  the  manufacture 
of  illuminating  gas,  and  metallurgical  coke. 

The  cost  of  briquettes  by  this  method  is  said  to  be  as 


PATENT   FUEL.  43 

follows :  If  culm  or  dust  from  a  good  coal,  valued  at  $1.20 
per  ton  (France  =  2,  205  pounds),  be  taken  for  their  manu- 
facture, six  per  cent  of  the  mixture  would  be  sufficient. 
The  price  of  a  ton  of  briquettes  would  be : 

94  per  cent  coal         2,073  pounds  @  6  cents  =  $i.  24 

6       "          mixture    132       "       @,  60    "     =         79 

Labor 40 

Total  cost  per  ton  =  $2.43 

It  is  claimed  that  the  heating  power  of  these  briquettes 
exceeds  that  of  average  coal  by  at  least  25  per  cent. 

Q.  What  is  patent  fuel  ? 

Patent  fuel  is  a  term  much  used  in  Europe  to  designate 
compressed  fuels  as  a  class.  Numerous  patents  have  been 
taken  out  for  producing  a  good  fuel  by  mixing  various  sub- 
stances with  small  coal,  in  proportions  sufficient  to  enable 
the  mixture  to  be  pressed  into  a  coherent  block.  Various 
binding  materials  have  been  tried,  such  as  soluble  glass, 
asphalt,  turpentine.  Meal  from  potatoes  was  abandoned 
because  the  blocks  were  not  water-tight.  Coal  tar  (War- 
lick's  process)  was  tried  at  Swansea,  England,  the  blocks 
being  baked  after  compression,  whereby  a  quantity  of  tar 
was  recovered.  On  the  Continent  cellulose  (German  pat- 
ent) and  treacle  (crude  molasses)  have  been  tried.  Pitch 
made  from  coal  tar  has  been  used  for  many  years  with 
great  success. 

In  the  dry  process  small  coal  is  carried  by  an  elevator 
into  a  large  bunker,  whence  it  is  lifted  by  another  ele- 
vator to  a  chute,  into  which  it  is  tipped  with  the  contents 
of  a  small  elevator  containing  pitch.  The  mixture  then 
passes  into  a  disintegrator,  and  the  resulting  product,  con- 
taining 8  to  1 2  per  cent  of  pitch,  passes  to  heaters,  and 


44  COMBUSTION   OF   COAL. 

finally  to  the  presses,  which  turn  out  100  to  200  blocks, 
weighing  10  to  30  pounds,  per  day  of  twelve  hours. 

In  the  steam  process  there  is  used  a  large  vertical  iron 
cylinder  with  arms  revolving  inside,  constantly  kept  fu)! 
of  a  mixture  of  pitch  and  coal.  High-pressure  steam  is 
injected  near  the  bottom  and  allowed  to  percolate  up 
through  the  mass,  while  the  arms  expose  every  portion  to 
its  action. 

Attempts  have  been  made  to  utilize  peat  by  mixing  it 
in  a  state  of  powder  with  small  coal  and  sawdust,  and 
pressing  the  mixture  into  blocks  (Thorpe). 

Q.  What  advantages  are  claimed  for  artificial  fuels? 

The  advantages  claimed  for  patent  fuels  over  ordinary 
coal  are  stated  to  consist — 

1.  In  their  efficacy  in  generating  steam. 

2.  In  occupying  less  space ;  that  is  to  say,  500  tons  of 
patent  fuel  may  be  stowed  in  an  area  which  will  contain 
only  400  tons  of  coal. 

3.  They  are  used  with  much  greater  ease  by  the  firemen 
than  coal,  and  they  create  little  or  no  dust  or  dirt,  con- 
siderations of  some  importance  where  no  bulkhead  sepa- 
rates the  fire-room  from  the  engine-room. 

4.  They  produce  a  very  small  proportion  of  clinkers, 
and  are  far  less  liable  to  choke  and  destroy  the  furnace 
grates  than  coal. 

5.  The  combustion  is  so  complete  that  comparatively 
little  smoke  and  only  a  small  quantity  of  ashes  are  pro- 
duced by  them. 

6.  From  the  mixture  of  the  patent  fuel  and  the  manner 
of  its  manufacture  it  is  not  liable  to  enter  into  sponta- 
neous ignition. 


PATENT   FUEL.  45 

Q.  What  is  the  composition  of  Grant's  patent  fuel  ? 

This  fuel  is  composed  of  coal  dust  and  coal-tar  pitch. 
These  materials  are  mixed  together,  under  the  influence  of 
heat,  in  the  following  proportions :  Twenty  pounds  of 
pitch  to  112  pounds  of  coal  dust,  by  appropriate  machin- 
ery, consisting  of  crushing  rollers  for  breaking  the  coal  in 
the  first  instance,  to  pass  through  a  one-fourth  inch 
screen;  secondly,  of  mixing  pans  or  cylinders  heated  to  a 
temperature  of  220°  F.,  either  by  steam  or  by  heated  air; 
and  thirdly,  of  moulding  machines  by  which  the  fuel  is 
compressed,  under  a  pressure,  equal  to  five  tons,  into  the 
size  of  a  common  brick.  The  fuel  bricks  are  then  white- 
washed, which  prevents  their  sticking  together,  either  in 
the  coal  bunkers  or  in  hot  climates. 

Q.  What  is  the  Strong  method  of  making  artificial 
fuel? 

The  combination  of  materials  and  processes  of  manufac- 
turing artificial  fuel  or  coal  briquette  by  R.  S.  Strong's 
method  is  to  wash  the  small  coal  in  order  to  free  the  same 
from  shale  and  dirt,  and  convey  it  from  the  drainers  to  a 
disintegrator  by  which  it  is  ground,  adding  about  2  per 
cent  of  fresh  calcined  powdered  alkaline  earth,  preferably 
lime,  in  order  to  absorb  the  moisture  in  the  coal.  To  this 
is  added  4  to  10  per  cent  (according  to  the  nature  of  the 
coal  or  the  purpose  for  which  the  fuel  is  intended)  of 
pyroligneous  acid,  preferably  from  a  steam-jacketed  tank. 
This  acid  is  the  whole  of  the  distillate  from  destructive 
distillation  of  wood  or  other  ligneous  substances  and  im- 
mediately absorbs  the  lime  and  solidifies  the  mixture, 
which  is  at  once  pressed  in  briquette  form  in  the  usual 
way,  and  on  leaving  the  press  may  be  cooled  by  a  fan  or 
blower  and  shipped  or  used  at  once. 


46  COMBUSTION   OF   COAL. 

In  carrying  out  the  process  with  unwashed  coal  only  one 
per  cent  or  less  of  the  caustic  alkaline  earth  is  used  to 
give  a  hook  to  the  pyroligneous  acid  to  act  on,  all  other 
treatment  being  as  before  described. 

Fuel  manufactured  as  described  is  suitable  for  house- 
hold, steam,  or  metallurgical  purposes,  and  burns  with  a 
clear  bright  flame,  and  is  produced  at  a  reasonable  cost. 

Q.  What  is  the  Corning  method  of  making  artificial 
fuel? 

In  the  working  of  the  Gardner  Corning  process  the 
binding  ingredients  employed  for  uniting  the  coal  dust 
into  briquettes  are  suitable  bitumens  and  quick  or  fresh- 
burned  lime.  Of  the  bitumens  natural  asphaltum  is  pre- 
ferred, although  the  artificial  bitumens,  such  as  the  by  or 
residual  products  of  petroleum,  are  suitable.  The  crude 
natural  asphaltum,  however,  is  too  brittle  for  the  purpose 
and  requires  tempering  by  the  admixture  of  some  artificial 
bitumen,  especially  a  residuum  oil  of  petroleum,  to  impart 
elasticity  and  tenacity.  To  properly  combine  the  coal 
dust  and  bitumen,  both  are  heated  to  as  high  temperature 
as  practicable  without  injury  by  burning  or  cooking.  By 
thorough  intermixture  while  thus  heated  the  thinnest  pos- 
sible film  or  coating  of  bitumen  is  given  to  the  dust  parti- 
cles to  secure  their  firm  adhesion  when  cooled.  The  pref- 
erable temperatures  employed  with  natural  asphaltum 
have  been  found  to  be  about  300°  F.  for  the  dust  and 
320°  to  340°  for  the  asphaltum.  If  other  bitumens  are 
used,  the  temperatures  may  be  varied  to  adapt  them  to  the 
different  melting  points  of  the  bitumens.  To  secure  the 
most  efficient  binding  action  of  the  lime,  it  is  slaked  with 
sufficient  water  to  make  a  liquid  mass  of  about  the  consist- 
ency of  cream,  and  which  is  therefore  known  as  "  cream 


PATENT    FUEL.  47 

of  lime."  This  is  intermixed  with  the  combined  dust  and 
bitumen  while  their  mass  is  still  hot,  and  this  step  of  the 
process  is  the  most  essential  part  of  the  method. 

The  proportions  of  the  ingredients  are :  Coal-dust,  about 
1,870  pounds;  bitumen,  about  80  pounds;  and  lime,  about 
50  pounds. 

Where  natural  asphaltum  is  employed,  about  5  pounds 
of  the  artificial  or  tempering  agent  is  mixed  with  about 
75  pounds  of  the  asphaltum. 

Either  anthracite,  bituminous,  or  lignite  coal  dust  may 
be  worked  by  this  process ;  but  the  best  results  have  been 
secured  by  combining  bituminous  dust  with  the  other. 

The  process  in  detail  is  as  follows :  The  coal  dust  is 
heated  to  the  requisite  temperature,  the  asphaltum  melted 
and  the  tempering  oil  mixed  with  it,  and  the  mixture 
heated  to  the  requisite  degree.  These  are  then  thorough- 
ly combined  in  a  mixer,  which  requires  usually  about 
three  minutes.  The  cream  of  lime  is  then  added  to  the 
hot  mass,  the  mixing  operation  being  continued  until  the 
water  begins  to  vaporize.  The  mass  is  then  delivered  to 
a  press  while  still  hot  and  moist,  and  formed  as  quickly  as 
possible  into  briquettes  under  heavy  pressure. 


CHAPTER  II. 

SOME   ELEMENTARY    DATA. 

PHYSICS. 
Q.  What  is  meant  by  the  term  work? 

Work  is  done  when  resistance  is  overcome.  If  a  force 
acts  upon  a  body  and  produces  motion  in  that  body,  the 
force  is  said  to  have  done  work ;  but  if  the  force  applied 
fails  to  produce  motion  in  the  body  thus  acted  upon,  no 
work  has  been  done  by  that  force.  The  work  done  by  a 
force  is  measured  by  the  product  of  the  force  into  the  dis- 
tance through  which  that  force  moves  in 'its  own  direction, 
or  work  =  force  X  distance. 

Q.  What  is  unit  of  work? 

The  unit  of  work  adopted  in  this  country  is  the  foot- 
pound, or  that  quantity  of  work  done  if  a  body  weighing 
one  pound  be  lifted  one  foot  high  against  the  action  of 
gravity.  The  foot-pound  is  a  gravitation  unit,  and  is 
wholly  independent  of  time. 

Q.  What  is  meant  by  lost  work  ? 

Of  the  work  put  into  a  machine  a  certain  portion  of  it 
must  be  expended  in  merely  keeping  the  different  parts  in 
motion,  and  the  work  thus  absorbed  is  lost  work.  The 
friction  diagram  of  a  steam-engine,  for  example,  represents 
so  much  lost  work,  inasmuch  as  it  is  necessary  to  overcome 
all  the  resistances  represented  by  the  diagram  before  any 


ELEMENTARY   DATA.  49 

useful  effect  can  be  obtained.     Lost  work  =  force  absorbed 
in  overcoming  internal  resistances  X  the  distance  it  acts. 

Q.  What  is  meant  by  useful  work? 

Useful  work  is  the  work  given  out  by  a  machine  after 
deducting  the  frictional  and  other  resistances  incident  to 
running  the  machine  empty  at  its  normal  speed.  Suppose 
a  steam-engine  should  indicate  220  H.  P.  and  the  friction 
diagram  of  the  engine  at  the  same  speed  indicated  25  H. 
P.,  the  useful  work  of  the  engine  would  be :  220  —  25  =  195 
H.  P.,  or,  as  it  is  sometimes  expressed,  the  net  horse 
power.  Useful  work  —  force  given  out  X  the  distance  it 
acts. 

Q.  What  is  meant  by  the  term  power? 

Power  is  the  rate  of  doing  work.  It  is  not  the  same. as 
force ;  it  is  not  the  same  as  pressure,  because  force  and 
pressure  act  independently  of  time ;  but  time  is  an  essen- 
tial element  when  estimating  the  quantity  of  work  done  by 
a  man  or  by  a  machine. 

Q.  What  is  the  unit  of  power  ? 

The  unit  of  power  in  mechanical  engineering  is  called 
the  horse  power.  It  is  the  rate  of  doing  work  at  33,000 
foot-pounds  per  minute. 

Q.  How  did  the  horse-power  unit  originate  ? 

James  Watt  ascertained  by  experiment  that  an  average 
cart  horse  could  develop  22,000  foot-pounds  of  work  per 
minute ;  and  being  anxious  to  give  good  value  to  the  pur- 
chasers of  his  engines,  he  added  50  per  cent  to  this 
amount,  thus  obtaining  (22,000  +  1 1,000)  the  33,000  foot- 
pounds per  minute  unit,  by  which  the  power  of  steam  and 
other  engines  has  ever  since  been  estimated  (Jamison). 
4 


50  COMBUSTION   OF   COAL. 

Q.  What  is  meant  by  the  term  energy? 

Energy  is  commonly  explained  as  the  capability  of  do- 
ing work,  and  by  doing  work  is  meant  overcoming  resist- 
ance. Energy  is  of  two  types,  known  as  kinetic  and  poten- 
tial ;  but  more  specifically  we  have : 

1.  Kinetic  energy. 

2.  Gravitation  energy. 

3.  Heat. 

4.  Energy  of  elasticity. 

5.  Cohesion  energy. 

6.  Chemical  energy. 

7.  Electrical  energy. 

8.  Magnetic  energy. 

9.  Radiant  energy. 

This  list  includes  all  known  separate  forms. 

Q.  What  is  potential  energy? 

Potential  energy  is  the  energy  due  to  position,  or  that 
form  of  energy  which  a  body  possesses  in  virtue  of  its 
condition.  Energy  due  to  position  may  be  illustrated  in 
the  case  of  a  weight,  say  50  pounds  raised  10  feet  high. 
This  would  represent  a  potential  energy  of  50  X  10  =  500 
foot-pounds,  because  if  liberated  it  would  through  proper 
means  accomplish  that  quantity  of  work.  This  can  be 
considered,  in  the  case  of  falling  bodies,  as  gravitation 
energy.  Energy  due  to  condition  may  be  illustrated  in 
the  case  of  the  coiled  spring  of  a  clock,  which  when  wound 
up  can  do  work  in  driving  the  train  of  mechanism,  an  ex- 
ample of  energy  due  to  the  elasticity  of  the  steel  spring. 
Coal  when  burned  under  proper  conditions  gives  out  heat 
which  may  be  utilized  for  generating  steam  and  doing 
work  through  the  medium  of  a  steam-engine. 


ENERGY.  51 

Q.  What  is  kinetic  energy? 

Kinetic  energy  is  the  energy  due  to  motion.  It  is  not 
easy  to  conceive  of  energy  apart  from  motion,  and  this  has 
led  some  physicists  to  the  conclusion  that  all  energy  is 
probably  kinetic. 

Q.  Are  the  two  types  of  energy,  kinetic  and  potential, 
mutually  independent? 

The  energy  of  motion  and  the  energy  of  position  or  con- 
dition are  being  continually  changed  one  into  the  other. 
The  conversion  of  one  form  of  energy  to  another  is  seen 
in  a  head  of  water  employed  to  turn  a  water  wheel.  The 
water  possesses  energy  due  to  its  height  above  the  wheel. 
The  weight  of  the  water  impinging  against  the  buckets  of 
the  wheel  gives  it  motion  and  is  thus  capable  of  doing 
work. 

Q.  What  is  the  great  characteristic  of  enegy? 

That  it  may  be  transformed  or  transmuted  from  one 
kind  of  energy  into  another  kind  of  energy;  but  through 
all  its  transformations  the  quantity  present  always  remains 
the  same,  though  known  by  different  names,  which  after 
all  are  but  those  of  convenience  in  classification.  It  has 
been  suggested  that  each  form  of  energy  arises  from  a 
mode  of  motion  of  some  portion  or  portions  of  substances 
or  of  matter,  and  that  therefore  all  energy  is  kinetic. 

Q.  What  is  meant  by  transmutation  of  energy? 

By  transmutation  of  energy  is  meant  the  changing  of 
one  kind  of  energy  into  another.  There  are  many  varie- 
ties of  visible  energy,  but  there  is  energy  which  is  invis- 
ible ;  and  the  one  may  be  converted  into  the  other.  The 
most  common  illustration  of  this  is  the  conversion  of  work 


52  COMBUSTION   OF  COAL. 

into  heat.  This  occurs  when  motion  is  arrested,  whether 
by  percussion  or  by  friction.  It  is  the  conversion  of  vis- 
ible or  actual  energy  into  heat ;  that  is,  into  molecular  or 
invisible  energy. 

Q.  What  is  meant  by  energy  of  fuel  ? 

Its  capacity  to  do  work.  Taken  altogether  the  heating 
power  of  coals  will  range  ordinarily  from  13,000  to  14,300 
heat  units  per  pound.  The  energy  of  fuel  or  its  power  to 
do  work  may  be  easily  computed  thus : 

Suppose  a  sample  of  coal  to  equal  14,000  heat  units  per 
pound ;  this  multiplied  by  772,  the  thermal  unit  known  as 
Joule's  equivalent,  we  have:  14,000  X  772  =  10,808,000 
pounds  raised  one  foot  high  in  one  minute,  this  represent- 
ing the  potential  energy  of  one  pound  of  coal.  It  will  be 
understood  that  the  above  represents  the  maximum  limit 
of  work  done  by  the  complete  combustion  of  one  pound  of 
coal,  an  amount  of  energy  expressed  in  foot-pounds  of 
work,  far  beyond  any  means  at  our  command  for  its  com- 
plete utilization. 

Q.  Can  energy  be  transferred  from  one  form  into 
another  without  loss? 

This  is  quite  impossible;  and  it  must  not  be  supposed 
that  the  various  forms  of  energy  may  be  transformed  into 
mechanical  energy  or  made  to  do  work  without  loss  in- 
cident to  the  absorption  by  the  various  other  forms  of 
energy  which  are  contiguous,  and  which  are  constantly 
seeking  fresh  supplies  of  energy  from  a  higher  source  than 
their  own.  If  these  processes  were  not  only  transformable 
but  reversible,  then  perpetual  motion  would  be  a  fact. 
We  know  that  heat,  as  a  form  of  visible  mechanical 
energy,  is  available  only  as  we  use  it  from  a  higher  to  a 


DISSIPATION   OF  ENERGY.  53 

lower  temperature;  and  we  know  further  that  once  the 
heat  has  spent  its  energy  or  capacity  for  doing  work,  there 
is  no  way  by  which  it  can  be  restored.  Heat  may  be 
made  to  do  work,  and  work  may  be  transferred  into  heat, 
but  the  processes  are  not  reversible. 

Q.  What  is  meant  by  dissipation  of  energy? 

The  principle  of  dissipation  of  energy  is  that  as  any 
operation  going  on  in  nature  involves  a  transformation  of 
energy,  and  transformation  involves  a  certain  amount  of 
degradation  (degraded  energy  meaning  energy  less  capable 
of  being  transformed  than  before),  energy  is  therefore  con- 
tinually becoming  less  and  less  transformable.  As  these 
changes  are  constantly  going  on  in  nature,  the  energy 
must  of  necessity  be  getting  lower  and  lower  in  the  scale, 
so  that  its  ultimate  form  must  be  that  of  heat  so  diffused 
as  to  give  all  bodies  the  same  temperature.  In  order  to 
get  any  work  out  of  heat,  it  is  absolutely  necessary  to  have 
a  hotter  body  and  a  colder  one ;  but  if  all  the  energy  be 
transformed  into  heat,  and  if  it  be  in  all  bodies  at  the 
same  temperature,  then  it  is  impossible  to  raise  the  small- 
est part  of  that  energy  into  a  more  available  form. 

Q.  What  is  a  thermometer  ? 

A  thermometer  is  an  instrument  for  measuring  tempera- 
tures constructed  upon  the  principle  of  the  expansion  of 
bodies  by  heat. 

It  consists  in  its  common  form  of  a  glass  tube  termi- 
nating in  a  bulb  containing  mercury,  which  fills  the  bulb 
and  part  of  the  tube ;  and  the  rise  or  fall  of  the  mercury 
in  the  tube,  according  as  the  mass  of  it  in  the  bulb  ex- 
pands or  contracts,  indicates  any  change  of  temperature  in 
the  surrounding  medium. 


54  COMBUSTION   OF  COAL. 

Q.  Why  is  mercury  commonly  used  for  indicating 
temperatures  in  a  thermometer  ? 

For  general  purposes  mercury  is  the  most  suitable  sub- 
stance for  use  in  thermometers  because  the  range  between 
its  points  of  solidification  and  ebullition  is  greater  than 
that  of  any  known  fluid.  It  is  also  a  good  conductor  of 
heat,  and  is  consequently  rapid  in  its  indications  and  sen- 
sitive to  sudden  changes  of  temperature.  Liquids  are 
progressively  more  expansive  at  higher  than  at  lower  tem- 
peratures ;  but  in  the  case  of  mercury  the  higher  expan- 
sion at  higher  temperatures  is  less  than  in  any  other  fluid 
body.  Hence  it  is  better  adapted  than  any  of  them  for 
the  construction  of  thermometers. 

Q.  What  are  the  limiting  temperatures  of  a  mercury 
thermometer  ? 

Mercury  freezes  at  —40°  F.  and  boils  at  600°  F.  Re- 
liable readings  of  temperature  of  a  mercury  thermometer 
are  therefore  limited  between  —30°  to  550°  F. 

Q.  What  constants  are  employed  when  fixing  standards 
of  temperature? 

In  order  to  measure  temperature,  certain  fixed  tempera- 
tures must  be  determined  upon.  The  constants  generally 
employed  are  the  melting  point  of  ice  and  the  boiling 
point  of  water  at  the  average  atmospheric  pressure. 

Q.  What  is  absolute  zero? 

The  absolute  zero  of  temperature  may  be  defined  as  the 
temperature  corresponding  to  the  disappearance  of  gaseous 
elasticity.  It  has  been  fixed  by  reasoning,  and  has  never 
been  measured.  The  law  of  expansion  of  a  perfect  gas  is 
that,  the  temperature  remaining  the  same,  its  volume  is 
inversely  proportional  to  the  pressure  of  the  gas ;  so  also, 


THERMOMETER.  55 

the  pressure  remaining  the  same,  the  volume  of  the  gas 
will  be  proportional  to  the  temperature. 

The  rate  of  expansion  of  a  perfect  gas  per  degree  is 
0.00203  at  32°  F.,  so  that  for  each  degree  in  rise  of  tem- 
perature the  gas  increases  -^-g  in  volume,  therefore  the 
volume  of  the  gas  would  be  doubled  if  its  temperature  be 
raised  493°  F.  This  law  holds  good  above  the  freezing 
point,  there  is  no  reason  for  doubting  that  it  holds  equal- 
ly good  for  temperatures  below  freezing;  we  have  then 
—  493  less  32  =  —461°  F.  as  the  absolute  zero  of  tem- 
perature. 

Q.  What  are  the  two  thermometric  scales  in  common 
use  ? 

The  two  thermometric  scales  in  common  use  are  the 
Fahrenheit  and  the  Centigrade.  The  zero  point  in  the 
Fahrenheit  scale  corresponds  to  that  temperature  obtained 
by  a  mixture  of  snow  and  salt,  which  is  marked  32°  below 
the  freezing  point  of  water.  The  height  of  the  mercury 
at  the  boiling  point  of  water  at  atmospheric  pressure  hav- 
ing been  marked  on  the  scale,  the  whole  distance  between 
the  freezing  and  the  boiling  point  of  water  is  divided  into 
1 80  equal  parts,  called  degrees,  and  this  graduation  is  con- 
tinued to  the  zero  point,  the  whole  number  of  degrees 
=  i8o-|-  32  —  212. 

The  Centigrade  scale  has  its  zero  at  the  freezing  point 
of  water,  and  the  interval  between  the  freezing  and  the 
boiling  points  of  water  at  atmospheric  pressure  is  divided 
into  100  equal  parts  called  degrees. 

The  freezing  point  of  water  is  32°  on  the  Fahrenheit 
scale,  and  o°  on  the  Centigrade.  The  boiling  point  of 
water  at  atmc  spheric  pressure  is  212°  on  the  Fahrenheit 
scale  and  100°  on  the  Centigrade. 


5<5 


COMBUSTION    OF    COAL. 


TABLE  7. — CENTIGRADE  TEMPERATURES    WITH    CORRESPONDING  TEM- 
PERATURES ON  THE  FAHRENHEIT  SCALE. 


Cent. 

Fahr. 

Cent. 

Fahr. 

Cent. 

Fahr. 

Cent. 

Fahr. 

-  40 

-  40 

6 

42.8 

52 

125.6 

98 

208.4 

~  39 

-38.2 

7 

44-6 

53 

127.4 

99 

2IO.2 

-  33 

-36.4 

8 

46.4 

54 

129.2 

100 

212.0 

—  37 

-34-6 

9 

48.2 

55 

131.0 

101 

213.8 

-  36 

—  32.8 

10 

50.0 

56 

132.8 

IO2 

215.6 

-  35 

-  3i 

ii 

5i.8 

57 

134.6 

I03 

217-4 

—  34 

—  29.2 

12 

53-6 

58 

136.4 

104 

219.2 

-  33 

-  27.4 

13 

55.4 

59 

138.2 

105 

221.0 

—  32 

—  25.6 

14 

57-2 

60 

140.0 

1  06 

222.8 

—  31 

-23.8 

15 

59-0 

61 

141.8 

107 

224.6 

—  30 

—  22 

16 

60.8 

62 

143.6 

108 

226.4 

-  29 

—  20.  2 

17 

62.6 

63 

145-4 

109 

228.2 

-  28 

-  18.4 

18 

64.4 

64 

147.2 

no 

230.0 

-  27 

-  16.6 

19 

66.2 

65 

149.0 

in 

231.8 

-  26 

—  14.8 

20 

68.0 

66 

150.8 

112 

233.6 

—  25 

-  13 

21 

69.8 

67 

152.6 

H3 

235-4 

-  24 

—  II.  2 

22 

71.6 

68 

154-4 

114 

237.2 

-  23 

-  9-4 

23 

73-4 

69 

156.2 

U5 

239.0 

—  22 

-  7-6 

24 

75-2 

70 

158.0 

116 

24O.8 

—  21 

-  5-8 

25 

77.o 

7i 

159.8 

117 

242.6 

—  20 

—  4 

26 

78.8 

72 

161.6 

118 

244.4 

—  19 

—   2.2 

27 

80.6 

73 

163.4 

119 

246.2 

-  18 

-  0.4 

28 

82.4 

74 

165.2 

120 

248.0 

—  17 

1-4 

29 

84.2 

75 

167.0 

121 

249.8 

-  16 

3-2 

30 

86.0 

76 

168.8 

122 

251.6 

—  15 

5.o 

31 

87.8 

77 

170.6 

123 

253-4 

-  14 

6.8 

32 

89.6 

78 

172.4 

124 

255-2 

—  13 

8.6 

33 

91.4 

79 

174.2 

125 

257-0 

—  12 

10.4 

34 

93-2 

80 

176.0 

126 

258.8 

—  II 

12.2 

35 

95.o 

81 

177-8 

127 

260.6 

—  IO 

14.0 

36 

96.8 

82 

179.6 

128 

262.4 

—  9 

15.8 

37 

98.6 

83 

181.4 

129 

264.2 

-  8 

17.6 

38 

100.4 

84 

183.2 

130 

266.O 

—  7 

19.4 

39 

IO2.2 

85 

185.0 

131 

267.8 

-  6 

21.2 

40 

IO4.O 

86 

186.8 

132 

269.6 

—  5 

23.0 

4i 

105.8 

87 

188.6 

133- 

271.4 

24.8 

42 

107.6 

88 

190.4 

134 

273-2 

—  3 

26.6 

43 

109.4 

89 

192.2 

135 

275.0 

—   2 

28.4 

44 

III.  2 

90 

194.0 

I36 

276.8 

—   I 

30.2 

45 

H3.0 

91 

195.8 

137 

278.6 

0 

32.0 

46 

H4.8 

92 

197.6 

138 

280.4 

I 

33.8 

47 

116.6 

93 

199.4 

139 

282.2 

2 

35-6 

48 

118.4 

94 

201.2 

140 

284.0 

3 

37.4 

49 

1  20.  2 

95 

203.0 

141 

285.S 

4 

39-2 

50 

122.0 

96 

204.8 

142 

287.6 

5 

41.0 

51 

123.8 

97 

2O6.6 

143 

289.4 

For  other  temperatures 
Cent.  -}~  32  =  deg.  Fahr. 


(Deg.   Fahr.  —  32)  X  f  =  deg.  Cent. ;  f  deg. 


THERMOMETER.  57 

Q.  How  may  the  temperature  readings  on  the  Fahren- 
heit and  Centigrade  scales  be  interconverted  ? 

The  distance  between  the  freezing  and  the  boiling  point 
of  water  is,  of  course,  the  same  for  both  thermometers,  but 
the  Fahrenheit  scale  contains  1 80  divisions  while  the  Cen- 
tigrade scale  contains  only  100  divisions  between  these  two 
points.  If  these  numbers  are  divided  by  20,  we  have  9 
and  5  respectively;  smaller,  therefore  more  convenient 
numbers  to  be  used  in  the  conversion  of  one  scale  into  the 
other.  The  zero  point  of  the  Fahrenheit  scale  is  32°  be- 
low the  freezing  point  of  water. 

To  convert  one  scale  into  the  other  is  quite  simple, 
thus: 

Fahr.  =  32  -[-  f  Cent,  degrees,  or 
Cent.  =  |  (Fahr.  degrees  —  32). 

frhat  is,  add  32°  to  f  of  the  number  indicated  on  the  Cen- 
tigrade scale  and  the  result  is  the  number  which  would  be 
indicated  by  the  Fahrenheit  scale.  Subtract  32°  from  the 
number  indicated  on  the  Fahrenheit  scale,  and  |-  of  the 
remainder  is  the  number  which  would  be  indicated  by  the 
Centigrade  scale. 

Example  i .  What  would  be  the  Fahrenheit  temperature 
corresponding  to  1 30°  C.  ? 

32 +f  of  130  =  266°  F. 

Example  2.  What  would  be  the  Centigrade  tempera- 
ture corresponding  to  266°  F.  ? 

|  of  (266  —  32)  =  130°  C. 

Q.  Does  a  thermometer  indicate  the  quantity  of  heat  in 
a  substance  ? 

It  does  not.  The  use  of  a  thermometer  is  merely  to 
indicate  the  sensible  heat,  or  that  which  is  capable  of  be- 


58  COMBUSTION   OF  COAL. 

ing  radiated  or  communicated  from  one  material  to  another. 
Its  indications  are  merely  relative  and  do  not  express  the 
actual  amount  of  heat  which  a  substance  contains. 

CHEMISTRY. 
Q.  What  is  an  atom  ? 

The  atomic  theory  affirms  that  every  portion  of  matter 
of  sensible  size  is  built  up  of  a  vast  number  of  small  par- 
ticles which  are  not  themselves  capable  of  further  subdi- 
vision. Each  particle  corresponding  to  this  definition 
would  be  called  an  atom  (a  term  borrowed  from  the  Greek), 
and  means  indivisible.  In  chemistry  it  means  the  small- 
est quantity  by  weight  of  an  element  which  is  capable  of 
existing  in  a  chemical  compound. 

Q.  What  is  meant  by  atomic  weight? 

One  of  the  properties  of  matter  is  that  it  has  weight ; 
atoms,  therefore,  have  weight  because  an  atom  is  a  defi- 
nite and  fixed  quantity  of  matter.  Hydrogen,  being  the 
lightest  known  substance,  has  by  general  consent  been 
made  the  unit  of  comparison ;  the  atomic  weight  of  hydro- 
gen is  always  represented  by  i . 

TABLE  8. — ATOMIC  AND  COMBINING  WEIGHTS  OF  GASES. 


Element. 

Atomic  weight. 

Combining  weight. 

Hydrogen 

I 

14 
16 

12 

f 

3 

Oxvcren 

Carbon  (diamond  burnt  to  CO2)  .... 

By  combining  weight  is  here  meant  the  smallest  mass 
of  the  element  which  combines  with  eight  parts  by  weight 
of  oxygen,  or  one  part  of  hydrogen. 


MOLECULE. 

TABLE  9. — ATOMIC  WEIGHTS. 


59 


Name. 

Symbol. 

Atomic  weights. 

Calcium      .  .      .  .               

Ca 

40 

Carbon  .    .            

c 

12    - 

Hydrogen 

H 

I 

Nitrogen 

N 

14 

Oxvtren 

O 

16 

Phosphorus           .  .                  *     ... 

P 

31 

Potassium                                   

K 

39 

Silicon                                   

Si 

28.5 

Na 

23 

Sulphur  .  .                   

S 

32 

The  above  list  of  elements  are  those  commonly  found  in 
coal  by  elementary  analysis.  Aluminum  and  iron  are  also 
found  in  the  analysis  of  coal  ashes. 

Q.  What  is  a  molecule  ? 

A  molecule  is  the  smallest  possible  portion  of  a  particu- 
lar substance,  whether  elementary  or  compound,  which 
exhibits  the  characteristic  properties  of  that  substance. 
Every  substance,  therefore,  whether  simple  or  compound, 
has  its  own  molecule;  and  if  this  molecule  be  divided,  its 
parts  are  molecules  of  a  different  substance  or  substances 
from  that  of  which  the  whole  is  a  molecule.  An  atom  is 
the  smallest  particle  of  an  element  which  enters  into  the 
composition  of  molecules.  In  the  case  of  the  molecule  of 
an  element  the  atoms  are  all  of  one  kind ;  in  the  case  of 
the  molecule  of  a  compound  the  atoms  are  of  two  or  more 
than  two  different  kinds.  As  the  properties  of  the  mole- 
cule of  a  compound  are  very  different  from  the  properties 
of  the  atoms  which  compose  it,  so  it  is  probable  that  the 
properties  of  the  molecule  of  an  element  are  different 
from  the  properties  of  the  atoms  by  the  union  of  which 
the  molecule  is  produced. 


6O  COMBUSTION    OF  COAL. 

Q.  What  is  one  of  the  characteristics  of  molecules? 

That  they  are  always  in  motion.  These  motions  of 
molecules  are,  in  the  case  of  solid  bodies,  confined  within 
so  narrow  a  range  that  even  with  our  best  microscopes  we 
cannot  detect  that  they  alter  their  places  at  all ;  but  in  the 
case  of  liquids  and  of  gases  the  molecules  are  not  confined 
within  any  definite  limits,  but  work  their  way  through  the 
whole  mass,  even  when  that  mass  is  not  disturbed  by  any 
visible  motion.  This  process  of  diffusion,  as  it  is  called, 
which  goes  on  in  gases  and  liquids  and  even  in  some 
solids,  can  be  subjected  to  experiment,  and  forms  one  of 
the  most  convincing  proofs  of  the  motion  of  molecules. 

Q.  What  is  meant  by  symbolic  notation  ? 

Symbolic  notation  belongs  to  an  agreed  employment,  as 
far  as  practicable,  of  the  first  letter  of  the  Latin  name  of 
an  element,  by  which  it  may  be  recognized  at  sight,  thus 
facilitating  the  representation  of  chemical  changes,  by 
which  reactions  of  a  complicated  character  may  be  under- 
stood at  a  glance.  Thus  carbon  is  represented  by  the  let- 
ter  C,  oxygen  by  O,  hydrogen  by  H,  etc.  Carbonic  oxide 
by  the  letters  CO ;  carbonic  acid  gas  by  the  formula  CO2, 
etc. 

Q.  Give  some  examples  of  the  symbolic  notation  of  com- 
pounds occurring  in  the  process  of  combustion  ? 

A  combination  of  elements  is  represented  by  a  combi- 
nation of  symbols  placed  side  by  side.  If  one  atom  of 
carbon  and  one  atom  of  oxygen  be  united  we  have  the 
symbol  CO,  carbonic  oxide.  It  will  be  understood  that 
one  atom  each  of  carbon  and  oxygen  unite  and  form,  not  one 
atom,  but  one  molecule  of  carbonic  oxide.  So  also  in  the 
previous  question  the  combination  of  one  atom  of  carbon 


SYMBOLIC   NOTATION.  6 1 

with  two  atoms  of  oxygen,  written  CO2,  is  the  symbolic 
expression  of  one  molecule  of  carbonic-acid  gas.  Hydro- 
gen is  represented  by  H;  its  atomic  weight  is  I.  The 
formula  H2O  means  that  two  atoms  of  hydrogen  have 
united  with  one  atom  of  oxygen  to  form  two  molecules  of 
water. 

Q.  Does  this  method  of  symbolic  notation  express  other 
than  an  abbreviation  of  the  name  of  an  element? 

Yes,  the  symbols  employed  are  not  only  abbreviations 
of  the  Latin  names  of  the  elements,  but  they  represent 
the  atomic  weights  of  the  several  elements  for  which  they 
stand.  Thus  carbon,  represented  by  C,  has  an  atomic 
weight  of  12  ;  and  as  there  is  no  other  element  having  an 
atomic  weight  of  12,  the  letter  C  and  figure  12  may  al- 
ways be  thus  associated.  It  will  be  understood  that  C 
always  stands  for  one  atom  of  carbon,  the  atomic  weight 
of  which  is  12  ;  and  if  more  than  one  atom  of  an  element 
appears  in  a  formula,  the  number  of  such  atoms  are  ex- 
pressed by  numerals,  thus :  CO2  for  carbonic  acid  gas, 
meaning  thereby  that  one  atom  of  carbon  and  two  atoms 
of  oxygen  have  entered  into  chemical  union. 

When  two  or  more  atoms  of  an  element  unite  in  the 
formation  of  a  molecule  of  a  compound  substance  the  writ- 
ten formula  is  simplified  by  writing  a  small  figure  to  the 
right  of  the  symbolic  letter  and  below  the  line.  Thus  C3 
indicates  three  atoms  of  carbon,  H8  indicates  eight  atoms 
of  hydrogen. .  The  formula  C3H8  indicates  one  of  the  prod- 
ucts of  coal  occurring  in  the  marsh  gas  series,  and  known 
as  propyl  hydride ;  and  this  formula  is  the  symbolic  ex- 
pression of  one  molecule. 

Secondary  compounds,  such  as  salts,  are  expressed  in 
an  analogous  way,  the  metal  being  usually  placed  first, 


62  COMBUSTION   OF  COAL 

CaCO3  representing  one  molecule  of  carbonate  of  calcium, 
calcium  being  the  metallic  base. 

Q.  What  is  meant  by  the  chemical  properties  of  a 
body? 

Those  which  relate  to  its  action  upon  other  bodies,  and 
to  the  permanent  changes  which  it  experiences  in  itself, 
or  which  it  effects  upon  them.  When  a  body  undergoes 
chemical  change  it  almost  invariably  destroys  the  physical 
properties  held  by  it  previous  to  this  change ;  but  experi- 
ment has  fully  demonstrated  that  matter  is  indestructible, 
so  that  whatever  changes  are  made  in  the  physical  appear- 
ance or  form  of  matter  by  any  chemical  process,  none  of 
it  is  destroyed. 

Q.  What  is  meant  by  affinity? 

By  affinity  is  commonly  meant  the  unknown  cause  of  the 
combination  of  atoms.  Hydrogen  and  chlorine  combine 
very  readily.  They  have,  as  we  say,  a  strong  affinity  for 
each  other;  yet  they  are  monovalent  with  reference  to 
each  other.  Carbon  and  chlorine  do  not  combine  readily. 
They  do  not  have  a  strong  affinity  for  each  other,  yet  an 
atom  of  chlorine  is  capable  of  holding  four  atoms  of  car- 
bon in  combination.  The  two  properties,  valency  and 
affinity,  are  possessed  by  every  atom,  and  exhibit  them- 
selves whenever  atoms  act  upon  one  another,  the  latter 
determining  the  intensity  of  the  reaction,  the  former  the 
complexity  of  the  resulting  molecule. 

Q.  What  is  meant  by  chemical  affinity  ? 

Chemical  affinity  is  that  property  of  bodies  in  virtue  of 
which,  when  brought  in  contact,  they  react  on  each  other, 
forming  new  bodies.  It  can  be  called  a  force,  in  so  far  as 


CHEMICAL  ATTRACTION.  63 

by  its  action  energy  is  produced — namely,  heat,  light, 
electrical  or  mechanical  energy;  and  vice  versa,  energy 
must  be  employed  to  reverse  the  action  of  chemical  affinity 
and  to  decompose  the  combined  substances.  Nothing  is 
known  as  yet  about  the  nature  of  chemical  affinity,  nor 
has  a  satisfactory  hypothesis  been  suggested  concerning  it. 

Q.  What  is  meant  by  chemical  attraction  ? 

Chemical  attraction  is  distinguished  from  other  chemi- 
cal forces  which  act  within  minute  distances  by  the  com- 
plete change  of  characters  which  follows  its  exertion,  and 
must  from  its  very  nature  be  exerted  between  dissimilar 
substances.  Hydrogen  and  oxygen  are  both  gaseous  and 
are  wholly  dissimilar  in  their  chemical  properties;  yet 
under  proper  conditions  they  will  unite  with  great  avidity, 
the  combination  forming  gaseous  steam,  which  upon  cool- 
ing yields  only  pure  water. 

The  physical  and  other  changes  brought  about  as  a  re- 
sult of  chemical  attraction  do  not  destroy  the  combining 
elements,  but  simply  rearrange  them  in  another  form,  and 
give  to  the  new  compound  properties  not  held  by  any  ele- 
ment singly. 

Q.  What  is  meant  by  the  term  equivalent  ? 

The  equivalent  of  an  element  is  that  mass  of  an  element 
which  combines  with  one  atom  of  hydrogen.  In  the  case 
of  oxygen  it  corresponds  to  half  an  atom,  in  that  of  nitro- 
gen to  one-third  the  atom,  and  in  that  of  carbon  to  one- 
fourth  the  atom.  With  those  elements  which  do  not  com- 
bine with  hydrogen  some  other  element  like  hydrogen  in 
respect  to  the  ratio  between  the  equivalent  and  atomic 
weight  is  taken  as  the  measure  of  the  equivalent. 


64  COMBUSTION   OF   COAL. 

Q.  What  law  governs  the  combining  weights  of  the 
elements  ? 

The  laws  of  chemical  combination  are  all  included  in 
the  two  statements:  i.  The  elements  combine  in  the  ra- 
tios of  their  combining  weights,  or  in  ratios  which  bear  a 
simple  relation  to  these.  2.  The  gaseous  elements  com- 
bine in  the  ratios  of  their  combining  volumes,  or  in  ratios 
which  bear  a  simple  relation  to  these. 

By  combining  weight  is  here  meant  the  smallest  mass 
of  an  element  which  combines  with  unit  mass  of  some 
specified  element  taken  as  a  standard ;  and  by  combining 
volume  is  meant  the  smallest  volume  of  a  gaseous  element 
which  combines  with  unit  volume  of  some  specified  gas- 
eous element  taken  as  a  standard.  The  first  statement  has 
been  amply  verified  by  accurate  experiment ;  the  second 
does  not  yet  stand  on  so  firm  an  experimental  basis. 

Q.  What  is  the  law  of  definite  proportions  ? 

The  law  of  definite  proportions  may  be  stated  thus :  In 
any  chemical  compound  the  nature  and  the  proportions  of 
its  constituent  elements  are  fixed,  definite,  and  invariable. 
For  example :  One  hundred  parts  of  water  by  weight  con- 
tain 88.9  of  oxygen  and  n.i  of  hydrogen.  These  gases 
will  combine  in  no  other  proportions  to  form  water,  and 
any  excess  of  either  gas  will  remain  unchanged. 

The  law  of  definite  proportion  assumes  that  atoms  have 
definite  weight ;  that  an  atom  is  a  fixed  and  definite  quan- 
tity; that  atoms  of  the  same  substance  are  of  the  same 
size  and  weight.  When  the  elements  unite  chemically, 
they  invariably  do  so  in  the  proportions  by  weight  repre- 
sented by  the  numbers  attached  to  them,  as  in  Table  9,  or 
in  multiples  of  these  numbers.  Dalton  accounted  for  this 
law  by  supposing  that  the  constituent  particles  of  matter  are 


MULTIPLE   PROPORTIONS.  6$ 

indivisible,  and  believed  that  if  it  were  possible  to  place 
such  particles  in  the  balance,  their  relative  weights  would 
be  found  to  correspond  with  the  numbers  given  in  the  table. 

Q.  What  is  the  law  of  multiple  proportions? 

When  two  or  more  compounds  are  formed  of  the  same 
elements,  there  is  no  gradual  blending  of  one  into  the 
other,  as  in  the  case  of  mixtures,  but  each  compound  is 
sharply  defined  and  exhibits  properties  distinct  from  those 
of  the  others,  and  of  the  elements  of  which  the  compounds 
are  composed.  For  example  : 

There  are  two  compounds  of  carbon  and  oxygen — 

Carbon        Oxygen          Atomic 
by  weight,    by  weight.       weight. 

Carbonic  oxide  CO 12  16  28 

Carbonic  acid  gas  COa 12  32  44 

It  will  be  observed  that,  the  quantity  of  carbon  remaining 
the  same,  the  quantity  of  oxygen  must  be  doubled  in  order 
to  form  the  other  compound.  These  proportions  consti- 
tute the  only  two  direct  inorganic  compounds  of  carbon  and 
oxygen. 

Q.  Is  the  atomic  value  of  an  element  changed  by  enter- 
ing into  chemical  combination  with  another  element? 

No,  the  atomic  value  of  each  element  in  a  compound 
remains  unchanged,  and  the  aggregate  weight  of  the  atoms 
forms  the  molecular  weight  of  the  compound  thus : 

One  molecule  of  carbonic  oxide  equals  : 

I  atom  of  carbon,  C,   at  wt.  12  =  12 
I  atom  of  oxygen,  O.  at  wt.    16  =  16 

Weight  of  one  molecule  CO    =  28 

One  molecule  of  carbonic-acid  gas  equals  : 

1  atom  of  carbon,  C,  at  wt.  12  —  12 

2  atoms  of  oxygen,  O,  at  wt.  16  =  32 

Weight  of  one  molecule  CO2   =  44 


66  COMBUSTION    OF   COAL. 

Q.  Is  chemical  attraction  influenced  by  temperature  ? 

In  all  cases  of  ordinary  combustion  it  is  essential  that 
the  temperature  of  the  uniting  substances  be  raised  to  the 
point  of  ignition.  A  mixture  of  oxygen  and  hydrogen 
may  be  preserved  unchanged  at  ordinary  temperatures  any 
length  of  time,  but  a  mere  spark,  or  the  introduction  of  a 
body  heated  to  redness,  so  completely  alters  their  mutual 
attraction  that  sudden  combination  attended  with  explosion 
is  the  result.  This  is  as  pure  a  case  of  augmentation  of 
chemical  attraction  as  can  be  met  with,  since  both  the 
components  are  thoroughly  mixed ;  and  as  both  are  perfect 
gases,  heat  cannot  in  this  case  act  by  diminished  cohesion, 
and  so  bring  their  particles  into  more  intimate  contact. 

Q.  What  is  meant  by  energy  of  chemical  separation  ? 

A  combustible  body  like  coal  may  be  taken  as  a  fair 
representative  of  potential  energy  because  it  occupies  a 
position  of  advantage  over  a  non-combustible  body  in  this, 
that  it  will  unite  with  another  body  for  which  it  has 
chemical  affinity  like  oxygen,  and  this  energy  of  position 
leading,  as  it  can  in  this  case,  to  a  process  of  chemical 
separation  during  the  act  of  burning,  in  which  we  have 
potential  energy  or  the  energy  possessed  by  the  coal  be- 
fore ignition,  and  the  energy  due  to  molecular  activity  by 
reason  of  the  act  of  combustion,  or  the  energy  of  motion 
changed  into  another  form  of  energy  represented  by  heat. 

The  energy  of  chemical  separation  when  produced  by 
the  combustion  of  coal  is  always  intense,  and  as  the  ob- 
served effects  are  so  much  below  the  theoretical  value 
ascribed  to  the  fuel,  it  would  seem  as  if  for  once  the  law 
of  conservation  of  energy  was  at  fault;  but  this  is  not  the 
case.  Our  methods  of  manipulation  are  wasteful  and  the 


ENERGY    OF   CHEMICAL   SEPARATION.  6? 

ordinary  construction  of  furnaces  so  faulty  that  a  very 
large  proportion  of  the  waste  can  be  directly  accounted 
for.  One  thing  with  reference  to  the  energy  of  chemical 
separation  is  certain,  and  that  is,  that  any  given  quantity 
of  carbon  or  other  combustible  under  given  conditions  will 
always  produce  the  same  quantity  of  heat. 


CHAPTER  III. 

THE   ATMOSPHERE. 

Q.  What  is  the  composition  of  air  ? 

The  composition  of  air  free  from  water  and  carbonic 
acid  is  found  to  be,  by  weight :  77  per  cent  of  nitrogen 
and  23  per  cent  of  oxygen ;  or  by  volume  :  79  volumes  of 
nitrogen  and  2 1  volumes  of  oxygen.  In  addition  to  these 
two  gases  atmospheric  air  contains  aqueous  vapor,  car- 
bonic acid,  ozone,  ammonia,  with  traces  of  nitrous  and  ni- 
tric acids,  etc. 

Air,  owing  to  the  oxygen  it  contains,  is  a  magnetic  sub- 
stance. 

Q.  Is  air  a  chemical  compound  ? 

It  is  not.  The  union  of  these  two  gases  in  the  propor- 
tions of  79  volumes  of  nitrogen  to  21  of  oxygen  gives 
common  air;  and  this  union  is  distinguished  by  no  proper- 
ties which  may  not  be  attributed  individually  to  these 
gases.  All  experiments  made  thus  far  have  shown  no  in- 
dication that  the  union  is  other  than  mechanical. 

Q.  What  proofs  sustain  the  statement  that  air  is  not  a 
chemical  compound  ? 

That  air  is  not  a  chemical  compound  of  its  component 
gases  is  proven  by  the  facts : 

i.  That  the  gases  nitrogen  and  oxygen  are  not  present 
in  any  constant  ratio. 


OXYGEN.  69 

2.  That  air  can  be  made  by  simply  mixing  its  constitu- 
ents in  the  proportion  indicated  by  the  analysis  of  air, 
without  contraction  or  any  thermal  disturbance  resulting. 

3.  That  on  treating  air  with  water  and  expelling  the 
dissolved  air  by  boiling,  the  proportion  of  the  oxygen  to 
the  nitrogen  is  found  to  be  increased,  and  in  amount  cor- 
responding with  the  law  of  partial  pressures. 

4.  That  the  constituents  of  the  air  can  be  mechanically 
separated  by  processes  of  diffusion. 

5.  That  the  refractive  power  of  the  air  is  equal  to  the 
mean  of  the  refractive  powers  of  its  constituents,  whereas 
in  compound  gases  the  refractive  power  is  either  greater 
or  less  than  the  refractive  power  of  the  elements  in  a  state 
of  mixture  (Thorpe). 

Q.  What  is  oxygen? 

Oxygen  is  present  in  the  atmosphere  in  a  free  and  un- 
combined  state,  forming  2 1  per  cent  of  its  total  volume. 
Priestly  first  obtained  the  gas  in  1774,  and  gave  it  the 
name  dephlogisticated  air.  It  was  isolated  independently 
and  almost  simultaneously  by  Scheele,  who  termed  it 
empyreal,  or  fire  air.  Lavoisier  regarded  it  as  an  essen- 
tial constituent  of  all  acids,  and  hence  gave  it  its  present 
name  oxygen.  The  discovery  of  oxygen  was  the  means  of 
leading  Lavoisier  to  the  true  theory  of  combustion. 

Oxygen  is  somewhat  heavier  than  the  air,  it  having  a 
specific  gravity  of  1.1056,  air  —  i.oooo.  One  hundred 
cubic  inches  of  oxygen  weigh  34. 206  grains.  The  specific 
heat  of  oxygen  for  equal  weights  at  constant  pressure  = 
0.2182;  for  constant  volume  —  0.1559.  When  pure, 
oxygen  is  colorless,  tasteless,  and  inodorous.  It  is  spar- 
ingly soluble  in  water.  As  with  all  gases  the  quantity 
dissolved  depends  on  the  tension  of  the  oxygen  in  the  at- 


70  COMBUSTION   OF  COAL. 

mosphere  in  contact  with  the  water.  Thus  pure  water 
shaken  up  in  contact  with  pure  oxygen  will  absorb  nearly 
five  times  as  much  oxygen  as  it  would  when  shaken  up,  at 
the  same  temperature  and  under  the  same  pressure,  with 
air,  which  only  contains  2 1  per  cent  by  volume  of  oxygen. 

Oxygen  is  the  least  refractive  of  all  the  gases.  It  is 
slightly  magnetic,  but  its  susceptibility  in  this  respect  is 
diminished  or  temporarily  suspended  by  elevation  of  tem- 
perature. 

Though  long  regarded  as  a  permanent  gas,  oxygen  was 
liquefied  in  1877  by  Pictet,  who  attributed  to  liquid  oxygen 
a  density  near  that  of  water,  about  0.9787.  The  critical 
temperature  of  oxygen  is  —113°  C.,  the  pressure  needed 
to  liquefy  it  at  that  temperature  being  about  50  atmos- 
pheres. Liquid  oxygen  is  a  pale,  steel-blue,  transparent, 
and  very  mobile  liquid,  boiling  at  — 181°  C.  at  ordinary 
pressures.  When  the  pressure  is  reduced  or  removed, 
evaporation  takes  place  so  rapidly  that  a  part  of  the  oxygen 
is  often  frozen  to  a  white  solid.  Liquid  oxygen  is  a  very 
perfect  insulator,  and  is  also  comparatively  inert  in  its 
chemical  properties. 

There  are  only  seven  elements  which  do  not  unite  di- 
rectly with  oxygen,  viz.,  fluorine,  chlorine,  bromine,  iodine, 
silver,  gold,  and  platinum.  All  the  non-metallic  elements 
with  two  exceptions  unite  with  oxygen  to  form  anhydrous 
acids.  Of  the  exceptions  hydrogen  forms  a  neutral  oxide 
(water),  while  no  oxide  of  fluorine  has  yet  been  obtained. 

The  product  of  the  union  of  oxygen  with  another  ele- 
ment is  called  an  oxide.  Thus  when  lead  is  heated  in 
contact  with  air  it  combines  with  oxygen,  forming  lead 
oxide,  PbO.  Carbon  burns  in  oxygen,  forming  carbon  di- 
oxide, CO2. 

The  chemical  activity  of  air  depends  upon  the  oxygen 


NITROGEN.  71 

it  contains,  air  being  simply  in  its  chemical  relations 
oxygen  diluted  with  nitrogen.  Free  oxygen,  whether  di- 
luted with  nitrogen  or  not,  manifests  considerable  chemi- 
cal activity,  even  at  ordinary  temperatures,  this  activity 
increasing  with  rise  of  temperature.  With  most  sub- 
stances an  initial  heating  is  necessary  to  start  free  oxida- 
tion, the  heat  evolved  being  then  sufficient  to  maintain  it. 
Various  substances  which  expose  large  surfaces  to  air  (or 
oxygen)  become  gradually  heated  through  slow  oxidation 
or  combustion ;  and  if  the  heat  cannot  get  away,  ignition 
eventually  occurs.  Thus  oily  or  greasy  woollen  and  cot- 
ton waste  or  rags  and  refuse  are  capable  of  absorbing 
oxygen  very  rapidly,  and  if  present  in  any  considerable 
quantity  the  heat  produced  may  accumulate  and  cause 
spontaneous  combustion;  and  this  action  is  a  not  infre- 
quent cause  of  fires  in  factories. 

Q.  What  is  nitrogen? 

Nitrogen,  one  of  the  most  widely  diffused  of  the  ele- 
ments, occurs  free  in  the  air,  of  which  it  constitutes  about 
79  per  cent  by  volume.  It  is  a  colorless,  inodorous,  taste- 
less, neutral  gas,  of  0.972  specific  gravity  (air  =  i);  100 
cubic  inches  at  60°  F.  and  30  inches  barometer  pressure, 
weigh  30.052  grains.  It  is  slightly  soluble  in  water; 
100  volumes  of  water  dissolve  1.5  volumes  of  nitrogen  at 
i  $°  C.  The  specific  heat  of  nitrogen  =  0.244,  at  constant 
pressure.  Nitrogen  has  been  liquefied  by  the  cold  pro- 
duced by  its  expansion  from  a  compression  of  300  atmos- 
pheres at  +13°  C.  Liquid  nitrogen  boils  at  —193°  C. 
under  atmospheric  pressure. 

Q.  Is  nitrogen  a  supporter  of  combustion  ? 

Nitrogen  is  incombustible,  and  does  not  support  com- 
bustion. Its  negative  qualities  are  very  pronounced ;  it 


72  COMBUSTION   OF   COAT.. 

will  not  take  fire ;  it  puts  out  the  combustion  of  every- 
thing, and  there  is  nothing  that  will  burn  in  it  in  ordinary 
circumstances.  It  is  not  a  poisonous  gas,  but  animal  life 
cannot  be  sustained  in  it  for  want  of  oxygen. 

Q.  Are  the  negative  qualities  of  nitrogen  a  hindrance 
in  furnace  combustion  ? 

The  useful  effect  of  nitrogen  in  combustion  is  that  it 
lowers  the  intensity  of  the  fire  and  makes  it  moderate, 
useful,  and  easily  controlled.  An  atmosphere  of  oxygen 
without  nitrogen  would  be  wholly  uncontrollable.  The 
iron  grate  and  furnace  front  would  burn  even  more 
powerfully  than  coal,  because  iron  is  more  combustible 
in  oxygen  than  is  carbon.  The  neutral  qualities  of  ni- 
trogen then  become  of  the  greatest  importance  in  com- 
bustion. 

Q.  Is  nitrogen  then  so  inert  that  it  will  not  combine 
with  other  substances  ? 

While  it  is  true  that  nitrogen  in  its  free  state  is  re- 
markable for  its  inactivity  in  furnace  combustion,  it  may 
be  made  to  unite  directly  under  certain  conditions  with 
hydrogen,  oxygen  and  carbon — as,  for  example,  when  a 
series  of  electric  sparks  is  passed  through  oxygen  and  ni- 
trogen gases,  standing  over  a  solution  of  caustic  alkali, 
when  a  nitrate  of  the  metal  is  produced.  Traces  of  nitric 
acid  and  ammonium  nitrate  are  produced  by  burning 
hydrogen  gas  mixed  with  nitrogen  in  an  atmosphere  of 
air  and  oxygen.  Nitrogen  can  unite  with  hydrogen  when 
one  or  both  of  the  gases  are  in  the  nascent  state,  to  form 
ammonia.  Carbon  and  nitrogen  unite  directly  when  ni- 
trogen gas  or  atmospheric  air  is  passed  over  an  ignited 
mixture  of  charcoal  and  potash. 


CARBONIC   ACID    IN   THE   AIR.  73 

Q.  What  economic  quality  does  nitrogen  display  in 
furnace  combustion? 

Nitrogen  in  its  ordinary  state  is  an  active  element,  not- 
withstanding its  negative  qualities  in  the  furnace.  No 
action  short  of  the  most  intense  electric  force,  and  then 
in  small  degree,  can  cause  the  nitrogen  to  combine  direct- 
ly with  the  other  element  of  the  atmosphere,  or  with 
things  round  about  it.  It  is  perfectly  indifferent,  and 
therefore  to  say  a  safe  substance.  The  part  which  nitro- 
gen plays  in  furnace  combustion  is  analogous  to  that  of  a 
vessel  in  which  the  oxygen  is  delivered  into  the  body  of 
incandescent  fuel.  The  oxygen  then  separates  from  the 
nitrogen  to  combine  with  the  carbon  of  the  fuel.  This 
delivery  having  been  made,  the  vessel  is  no  longer  of  any 
value  in  that  connection  and  passes  on  through  the  fire. 
By  reason  of  its  lighter  gravity  it  assists  in  maintaining  a 
good  draught,  a  matter  of  prime  importance  in  furnace 
combustion. 

Q.  What  quantity  of  carbonic  acid  is  present  in  the 
air  ? 

There  is  in  the  air,  besides  the  aqueous  vapor,  3.36 
parts  in  every  10,000  of  carbonic-acid  gas.  Any  circum- 
stance which  interferes  with  ready  diffusion  of  the  prod- 
ucts of  respiration  and  the  combustion  of  fuel  will  of 
course  tend  to  increase  the  relative  amount  of  carbonic 
acid  of  a  town ;  hence  during  fogs  the  amount  may  be  as 
great  as  o.  i  percent.  The  pressure  exerted  by  the  car- 
bonic acid  in  the  air  is  so  small  that  its  amount  is  not  per- 
ceptibly diminished  by  rain.  The  amount  is  also  not 
sensibly  altered  in  the  higher  regions  of  the  atmosphere. 

Q.  What  quantity  of  ammonia  is  present  in  the  air  ? 
Ammonia  is   present  in  the  air   in   minute  quantities 


74  COMBUSTION    OF   COAL. 

only;  it  exists  mainly  as  carbonate  and  is  subject  to  very 
great  variations  as  to  quantity.  Rain  water  collected  in 
towns  always  contains  large  quantities  of  ammonia,  prob- 
ably due  to  the  influence  of  animal  life  and  to  the  constant 
presence  in  greater  proportion  than  in  the  country  of  read- 
ily decomposable  nitrogenous  organic  matter  in  the  air. 

Q.  What  quantity  of  aqueous  vapor  is  present  in  the 
air? 

Aqueous  vapor  in  the  air  varies  in  quantity  with  the 
temperature ;  but  more  of  it  can  be  sustained  in  warm  air 
than  in  cold.  Air  at  a  temperature  of  32°  F.  can  sustain 
the  Y-J-g-  part  of  its  own  weight  of  aqueous  vapor,  but  at 
86°  F.  it  can  sustain  y^j-  part  of  its  own  weight.  The 
humidity  of  the  air  is  usually  estimated  by  means  of 
hygrometers.  The  barometer  gives  the  combined  weight 
of  the  oxygen,  nitrogen,  and  gaseous  vapor  of  the  air,  and 
the  portion  of  this  weight  which  is  due  to  aqueous  vapor 
is  called  the  elastic  force  of  vapor.  With  a  barometer 
standing  at  30  inches,  and  with  a  hygrometer  indicating 
an  elastic  force  of  vapor  of  .45,  very  nearly  one-fourth 
pound  of  the  entire  pressure  of  fifteen  pounds  is  due  to  the 
vapor.  When  more  vapor  is  generated  than  can  be  at 
once  carried  away,  the  barometer  necessarily  rises ;  when 
vapor  is  condensed  in  the  atmosphere  the  barometer  falls ; 
when  the  temperature  of  saturated  air  is  reduced  from  80° 
to  60°,  five  grains  of  aqueous  vapor  are  deposited  from 
each  cubic  foot.  This  is  the  effective  cause  of  rain. 

Q.  Is  ozone  always  present  in  the  air  ? 

Ozone  is  always  present  in  minute  quantities  in  normal 
air.  Atmospheric  ozone  is  probably  formed  by  the  action 
of  electricity  on  air  and  on  the  water  contained  in  it,  and 
by  the  evaporation  of  water.  It  appears  that  the  amount 


ATMOSPHERIC    PRESSURE.  75 

of  ozone  varies  with  the  seasons ;  it  is  greatest  in  spring, 
becomes  gradually  less  during  summer  and  autumn,  and  is 
least  in  winter.  Ozone  is  more  frequently  observed  on 
rainy  days  than  in  fine  weather.  Thunder  storms,  gales, 
and  hurricanes  are  frequently  accompanied  by  relatively 
strong  manifestations  of  it. 

Q.  What  is  the  weight  of  air? 

The  weight  of  one  cubic  foot  of  air  at  32°  F.  is  .080728 
pound,  or  565. 1  grains;  at  62°  F.  it  is  .076097  pound,  or 
532.7  grains.  The  volume  of  one  pound  of  air  at  32°  F. 
at  ordinary  atmospheric  pressure  (14.7  pounds)  is  12.4 
cubic  feet. 

Q.  What  is  atmospheric  pressure? 

Air  in  common  with  other  bodies  possesses  the  property 
of  weight ;  and  as  the  pressure  of  water  at  the  bottom  of  a 
tank  is  greater  than  near  its  upper  surface,  so  the  pressure 
of  the  atmosphere  is  greater  at  the  level  of  the  sea  than  at 
the  top  of  a  high  mountain.  We  are  not  certain  as  to  the 
height  of  the  atmosphere,  but  it  is  commonly  supposed  to 
be  not  less  than  forty-five  miles,  measured  from  the  sea 
level.  Whatever  its  height,  we  know  that  a  vertical  col- 
umn of  this  air  produces  an  average  pressure  on  the  earth's 
surface  of  about  14.73  pounds  per  square  inch;  but  the 
pressure  even  at  the  same  place  is  continually  varying 
from  a  variety  of  causes.  In  steam  engineering  the  press- 
ure of  the  atmosphere  is  commonly  assumed  to  be  fifteen 
pounds  per  square  inch. 

Q.  What  is  the  unit  of  pressure? 

The  unit  of  pressure  adopted  by  European  engineers  and 
others,  and  styled  an  atmosphere,  is  an  amount  equal  to  the 
average  pressure  at  the  level  of  the  sea.  In  British  meas- 


76  COMBUSTION    OF   COAL. 

ures  an  "atmosphere  "  is  the  pressure  equivalent  to  29.905 
inches  of  mercury  at  32°  F.  at  London,  and  is  about  14.73 
pounds  to  the  square  inch.  Steam  engineers  in  this  coun- 
try make  their  calculations  for  pressures  in  terms  of  pounds 
per  square  inch,  it  being  a  more  convenient  unit  than  an 
"atmosphere." 

Q.  How  is  the  pressure  of  the  atmosphere  measured? 

By  means  of  an  instrument  called  a  barometer;  one 
variety  of  which  consists  of  a  vertical  glass  tube  of  uni- 
form diameter,  hermetically  sealed  at  the  top  end,  and  of 
about  33  inches  in  length,  into  which  mercury  has  been 
poured  until  it  has  been  completely  filled  and  then  in- 
verted, its  lower  and  open  end  being  placed  in  a  vessel 
also  containing  mercury.  A  graduated  scale  reading  to 
inches,  and  by  means  of  a  vernier  to  hundredths  of  an 
inch  is  located  near  the  top  of  the  glass  tube  for  read- 
ing the  level  of  the  mercury.  The  pressure  of  the 
atmosphere  acting  on  the  surface  of  the  mercury  in  the 
open  vessel  causes  a  rise  or  fall  of  the  mercury  directly 
proportional  to  the  pressure  of  the  atmosphere. 

Q.  Is  the  atmosphere  of  the  same  density  throughout 
its  height? 

The  density  of  the  air  rapidly  diminishes  with  the 
height.  For  air  of  constant  temperature  its  density,  or 
what  comes  to  the  same  thing,  the  height  of  the  baro- 
metric mercury  column,  should  diminish  in  geometric  pro- 
gression, while  the  distance  from  the  earth  increases  in 
arithmetic  progression. 

Q.  How  does  the  law  of  Mariotte  and  Boyle  apply  in 
determining  the  density  of  the  air  ? 

Mariotte  and  Boyle  have  established  the  law  that  every 


HEATING   AND    COOLING   AIR.  77 

time  the  pressure  upon  air  is  doubled  its  volume  is  halved. 
This  is  the  obvious  reason  why  air  is  more  rare  and  light, 
bulk  for  bulk,  at  the  higher  regions  of  the  atmosphere 
than  it  is  near  the  surface  of  the  earth.  At  a  height  of  three 
miles  the  air  has  a  doubled  volume  and  half  its  original 
density.  It  is  again  doubled  in  volume  at  about  six  miles 
high ;  and  it  is  probable  that  no  animal  could  continue  to 
live  and  breathe  at  a  height  of  eight  miles. 

Q.  How  may  pounds  of  air  be  converted  into  an  equiv- 
alent volume  in  cubic  feet  ? 

As  we  have  no  convenient  means  for  weighing  air  in 
bulk,  and  as  air  is  known  to  weigh  532.7  grains  per  cubic 
foot  at  62°  F.,  it  will  be  a  near  enough  approximation  as 
between  summer  and  winter  temperatures  to  assume  that 
one  pound  of  air  =  12.  5  cubic  feet. 

Q.  May  air  be  readily  heated  and  cooled? 

The  difficulty  in  either  heating  or  cooling  air  is  its  non- 
conducting capacity;  or,  more  strictly  speaking,  the  diffi- 
culty in  obtaining  a  sufficiently  rapid  convection  of  heat 
to  and  from  the  mass  of  air  employed.  To  heat  or  cool 
air,  very  extensive  surfaces,  together  with  very  great  dif- 
ferences of  temperature,  are  necessary.  Siemen's  regener- 
ators have  about  17  pounds  of  fire  brick  for  each  increment 
of  gaseous  fuels  that  can  be  developed  from  one  pound  of 
coal.  As,  however,  only  about  one-fourth  of  the  total  re- 
generative capacity  is  being  heated  to  the  full  tempera- 
ture of  the  gases  passing  down  through  the  ports,  this 
amount  has  to  be  increased  fourfold,  so  that  nearly  70 
pounds  of  fire  brick  are  probably  used  per  pound  of  prod- 
uct of  combustion. 


78  COMBUSTION   OF  COAL. 

Q.  Does  the  density  of  the  air  affect  the  passage  of 
heat  through  it  ? 

An  interesting  phenomenon  relating  to  the  weight  or 
density  of  the  air  is  the  variation  in  what  is  known  as  its 
diathermancy,  or  heat  passing  through  it  without  being 
apparently  absorbed.  The  greater  the  tenuity  of  the  air, 
the  more  nearly  diathermanous  is  it.  Pure  air  is  virtually 
quite  pervious  to  heat ;  none  stops  in  the  air,  but  all  passes 
through.  The  absolute  diathermacy  of  dry  air  accounts 
for  the  scorching  heat  of  mountain  tops  as  the  retentive 
power  of  aqueous  vapor  does  for  the  soft  heat  of  low-lying 
regions  in  the  tropics. 

Q.  How  is  atmospheric  air  affected  by  heat? 

Air  is  expanded  by  increase  of  temperature,  the  increase 
in  volume  being  TJ-g-  part  for  each  degree  Fahrenheit.  For 
example,  1,000  cubic  inches  at  32°  F.  would  be  increased 
at  212°  to  1,336  cubic  inches. 

Q.  Why  is  it  necessary  to  provide  for  a  supply  of  air 
through  the  fuel  in  furnace  combustion  ? 

Atmospheric  air  is  the  only  available  source  of  oxygen 
for  supporting  the  combustion  of  fuels. 

Q.  What  is  the  physical  effect  of  heat  upon  the  air 
entering  the  fire  ? 

The  first  physical  effect  of  heat  upon  air  is  its  expan- 
sion, and  this  of  necessity  takes  place  in  the  most  confined 
space,  namely,  in  the  interstices  of  the  fuel,  and  acts 
equally  in  all  directions.  Although  all  in  motion  upward 
through  the  fire,  its  upward  portion,  being  most  greatly 
expanded,  is  moving  more  rapidly  than  its  less  expanded 
lower  portion ;  and  its  expansive  force,  acting  downward, 


HEATED    AIR   AND    COMBUSTION.  79 

simply  retards  the  upward  flow  of  entering  air.  Lateral 
expansion  aids  in  bringing  fresh  oxygen  into  contact  with 
unconsumed  carbon.  Upward  expansion  aids,  and  down- 
ward expansion  retards  the  draught.  Now  it  is  plain  that 
this  effect  must  be  the  greater  the  greater  the  degree  of  ex- 
pansion which  takes  place  within  the  interstices  of  the  fuel. 
With  air  supply  at  60°  F.  it  is  5. /-fold;  with  equal  air 
supply,  by  weight,  at  385  F.  it  is  3.  5-fold,  as  shown  on 
page  80. 

Q.  What  would  be  the  physical  effects  if  air  at  60° 
F.  be  heated  to  385°  F.  and  supplied  a  furnace  at  the 
latter  temperature  ? 

If  to  the  sensible  temperatures  60°  and  385°  we  add 
461°,  we  shall  have  the  corresponding  absolute  tempera- 
tures of  521°  and  846°  respectively;  and  the  volume  of 
the  heated  air  will  be  increased  in  the  ratio  of  these  two 
numbers,  or  |-|~|-  =  1.624.  Therefore  8  cubic  feet  of  air 
at  60°  would  occupy  8  X  1.624  =  12:992,  say  13  cubic  feet 
at  the  higher  temperature,  at  which  we  will  suppose  it  to 
be  conveyed  to  the  fire.  The  density  of  the  air  will  be 
in  the  same  inverse  ratio ;  that  is,  1 3  cubic  feet  of  air  at 
385°  must  be  admitted  to  the  fire  and  to  contact  with 
glowing  fuel  in  order  to  introduce  as  much  oxygen  as 
would  be  contained  in  8  cubic  feet  of  the  air  at  60°  F. 
Equally,  of  course,  the  entering  velocity  must  be  greater 
in  the  same  proportion,  since  the  aggregate  area  of  all  the 
orifices  through  the  grates  and  fuel  may  be  regarded  as 
constant.  This  has  been  urged  as  an  objection  to  heating 
air  before  its  introduction  to  the  fire. 

Q.  Is  the  increase  in  volume  due  to  preheating  air,  as 
suggested  above,  a  valid  objection  to  its  use  ? 

Cold  air  in  necessary  quantity  will  enter  the  ash  pit  and 


80  COMBUSTION   OF   COAL. 

will  pass  through  the  openings  in  the  grates  with  less 
velocity  than  will  the  same  quantity  of  heated  air.  But 
in  these  passages  the  area  is  amply  large  and  the  velocity 
moderate.  It  is  also  true  that  on  entering  the  lower 
stratum  of  fuel  the  velocity  of  the  heated  air  will  be  the 
greater.  The  very  first  effect  of  the  chemical  union  of 
any  part  of  the  oxygen  with  any  part  of  the  carbon  is  to 
heat  the  gases  associated  with  such  oxygen — that  is,  its 
associated  nitrogen  and  the  atmospheric  air  yet  containing 
its  oxygen,  together  with  the  carbonic-acid  gas  resulting 
from  such  union  or  combustion,  to  the  full  extent  to  which 
the  entire  heat  of  combustion  can  raise  the  given  mass  of 
gases.  This  will  approximate  the  temperature  of  the  fur- 
nace, modified  by  the  subsequent  union  of  further  portions 
of  oxygen  with  new  portions  of  carbon  encountered  during 
the  farther  progress  of  the  mixed  gases  through  the  fuel, 
until  they  emerge  at  the  surface  of  the  fire. 

If  their  temperature  be  now  2500°  F.  or  2961°  absolute, 
their  volume  will  be  -^^y1-— 5.7  times  that  of  the  air  tem- 
perature, 60°  F.,  and  2£f±—  3.5  times  that  of  air  of 
temperature  385°  F.  Now  it  is  this  volume  of  the  gases 
at  their  final  emergence  from  the  interstices  of  the  fuel 
that  determines  their  flow;  determines  the  force  of 
draft,  or  blower  required  to  produce  that  flow.  The 
difference  between  3.  5  times,  as  against  5.7  times,  is  favor- 
able and  compensates,  as  far  as  it  goes,  for  the  greater 
force  required  to  introduce  the  heated  air  with  its  greater 
volume  and  higher  velocity. 

Q.  What  are  the  combined  physical  and  chemical  effects 
of  heated  air  for  furnace  combustion  ? 

Carbon  and  oxygen  will  unite  at  all  temperatures  usually 
met.  Coals  waste  in  the  open  air  by  slow  combustion, 


QUANTITY    OF   AIR    REQUIRED.  8 1 

the  resulting  heat  being  dissipated  by  radiation  and  the 
convection  of  the  air.  The  rapidity  of  combustion  is  aug- 
mented with  the  rise  of  temperature,  and  is  very  great  at 
high  incandescence.  The  temperature  of  the  oxygen  is  no 
less  important  than  that  of  the  carbon ;  the  higher  the 
sum  of  their  temperatures,  the  more  rapid  is  their  union. 
So  far  as  the  associated  gases  are  concerned,  their  higher 
temperature  only  serves  to  communicate  more  heat  to  the 
mass,  or,  which  amounts  to  the  same  thing,  to  abstract 
less  heat  from  it.  With  heated  air  the  resulting  temper- 
ature is  higher  and  the  combustion  will  be  more  rapid. 

Q.  How  may  the  quantity  of  air  required  for  the  com- 
bustion of  any  fuel  be  determined  ? 

The  quantity  of  oxygen  required  for  the  complete  com- 
bustion of  any  given  quantity  of  carbon  or  hydrogen  has 
been  experimentally  determined  and  is  well  known ;  the 
quantity  of  oxygen  in  the  atmosphere  being  practically 
constant,  the  process  of  determining  the  amount  of  air  re- 
quired for  these  two  elements  is  quite  simple,  thus : 

One  pound  of  hydrogen  requires  8  pounds  of  oxygen  for 
its  complete  combustion ;  this  requires  about  36  pounds  of 
air. 

One  pound  of  carbon  requires  2^  pounds  of  oxygen  for 
its  complete  combustion  (to  CO2),  or  about  12  pounds  of 
air. 

One  pound  of  carbon  incompletely  burnt,  or  to  carbonic 
oxide  (CO),  requires  i%  pounds  of  oxygen,  or  about  6 
pounds  of  air. 

All  the  above  are  based  on  the  assumption  that  4.5 
pounds  of  air  are  required  to  supply  i  pound  of  oxygen. 

The  above  applies  only  to  such  fuels  as  have  undergone 
analysis,  the  elemental  constituents  being  known. 
6 


82 


COMBUSTION    OF    COAL. 


A  table  giving  the  theoretical  quantity  of  air  required 
for  a  variety  of  fuels  was  prepared  by  Rankine,  and  has 
very  general  acceptance.     This  table  is  here  reproduced. 
TABLE  10  — AIR  REQUIRED  FOR  PERFECT  COMBUSTION. 


Fuel. 

Carbon. 

Hydrogen. 

Oxygen. 

Air 
Required. 

I.   Charcoal,  from  wood  

O.Q3 

II   l6 

from  peat  

0.80 

Q.6 

II.  Coke  good 

O.  Q4 

1  1  28 

III.   Coal,  anthracite 

o  QIC; 

O  O^^ 

o  026 

12   17 

dry  bituminous.  .  .  . 

o  87 

O  O5 

o  04 

12  06 

caking  

-  0.85 

o  05 

o  06 

II   ~i"\ 

caking  

0.75 

O.O5 

O.O5 

10.58 

cannel 

o  84. 

o  06 

o  08 

ii  88 

dry  long  flaming 

O  77 

o  05 

O  1C 

10  32 

lignite 

o  70 

0.05 

O  2O 

9-2Q 

IV.    Peat,  dry   

0.58 

0.06 

O  "31 

7  68 

V.   Wood,  dry  

0.50 

6  oo 

VI.    Mineral  oil  

0.85 

15.65 

Q.  What  quantity  of  air  is  usually  estimated  per  pound 
of  coal ? 

The  theoretical  quantity  of  air  required  for  boiler  fur- 
naces is  assumed  to  be  12  pounds  of  air  for  each  pound  of 
coal,  regardless  of  its  composition.  From  18  to  24 
pounds  of  air  per  pound  of  coal  burnt  is  a  common  allow- 
ance when  making  up  estimates ;  24  pounds  of  air  is  a 
near  approximation  to  the  average  quantity  supplied  the 
burning  fuel  per  pound  of  coal. 

Q.  What  is  the  specific  heat  of  air  ? 

The  specific  heat  of  air  at  constant  pressure  is  0.2374 
(Regnault). 

Q,  Under  what  conditions  may  air  be  liquified? 

Under  the  critical  pressure  of  39  atmospheres,  and  at 
the  low  temperature  of  312°  below  the  Fahrenheit  zero 
(—  191°  C.),  air  may  be  liquefied. 


CHAPTER  IV. 

COMBUSTION. 

Q.  What  is  combustion  ? 

Any  manifestation  of  chemical  energy  attended  by  com- 
bination and  accompanied  by  production  of  much  heat  is, 
strictly  speaking,  an  instance  of  combustion.  In  steam 
engineering  it  means  the  controlled  chemical  combination 
of  the  elements  carbon  and  hydrogen  in  the  fuel  with  the 
oxygen  of  the  atmosphere,  by  which  an  evolution  of  heat 
is  secured  and  maintained  in  a  suitably  constructed  fur- 
nace for  the  purpose  of  generating  steam. 

The  term  combustion,  as  commonly  used,  carries  with 
it  the  idea  of  incandescence,  or  the  glowing  whiteness  of 
a  body  caused  by  intense  heat,  which  is  quite  character- 
istic of  burning  carbon;  the  term  also  includes  that  of 
inflammation,  which  is,  however,  best  restricted  to  in- 
stances of  combustion  in  which  the  incandescent  sub- 
stances are  gaseous.  All  phenomena  of  burning  are  in- 
stances of  combustion,  and  in  the  great  majority  of  cases 
they  consist  in  the  union  of  the  oxygen  of  the  atmosphere 
with  the  substance  which  is  being  burnt,  the  visible  signs 
of  combustion,  i.e.,  the  heat  and  light,  being  the  result  im- 
mediate or  proximate  of  the  chemical  energy  so  expended. 

Q.  What  is  the  nature  of  combustion  as  applied  par- 
ticularly to  coal? 

Coal  is  mainly  composed  of  the  two  elements,  carbon 
and  hydrogen,  both  of  which  have  an  affinity  for  oxygen ; 


84  COMBUSTION   OF   COAL. 

but  before  they  unite  chemically  to  produce  heat  it  is 
necessary  that  certain  conditions  be  fulfilled,  the  first  of 
which  is  that  a  considerable  mass  of  the  coal  must  be 
heated  to  the  point  of  ignition  before  the  oxygen  in  the 
air  will  unite  with  it. 

The  oxygen  having  a  choice  of  two  partners,  as  Profes- 
sor Tyndall  happily  puts  it,  closes  with  that  for  which  it 
has  the  strongest  attraction.  It  first  unites  with  the  hy- 
drogen and  sets  the  carbon  free.  Innumerable  solid  par- 
ticles of  carbon  thus  scattered  in  the  midst  of  burning 
hydrogen  are  raised  to  a  state  of  incandescence.  The  car- 
bon, however,  in  due  time,  closes  with  the  oxygen,  and 
becomes,  or  ought  to  become,  carbonic  acid.  The  light 
and  heat  produced  by  the  burning  of  coal  are  due  to  the 
collision  of  atoms  which  have  been  urged  together  by  their 
mutual  attractions. 

An  isolated  piece  of  coal  will  not  burn  in  the  open  air, 
because  the  temperature  will  soon  fall  below  the  point  of 
ignition,  consequently  chemical  action  will  cease;  but  an 
ignited  mass  of  coal,  as  in  a  furnace  or  a  stove,  will  give 
off  great  heat,  depending  upon  the  quality  and  quantity  of 
coal  burned;  but  once  the  hydrogen  having  united  with 
the  oxygen  to  form  water,  and  the  carbon  with  the  oxygen 
to  form  carbonic-acid  gas,  their  mutual  attractions  are  sat- 
isfied, and  all  the  heat  has  been  given  off  that  is  possible 
under  any  conditions. 

Q.  In  what  proportion  does  oxygen  unite  with  hydro- 
gen and  with  carbon  ? 

Oxygen  and  hydrogen  unite  in  the  ordinary  processes 
of  combustion  in  one  proportion  only,  viz. ,  two  atoms  of 
hydrogen  unite  with  one  atom  of  oxygen,  the  product  of 
the  combustion  being  aqueous  vapor,  or  water,  HaO. 


OXYGEN   A   SUPPORTER   OF   COMBUSTION.  8$ 

Oxygen  and  carbon  unite  in  the  ordinary  process  of 
combustion  in  two  proportions,  viz.,  one  atom  of  carbon 
and  two  atoms  of  oxygen,  the  product  being  carbonic-acid 
gas,  CO2;  and  one  atom  each  of  carbon  and  of  oxygen,  the 
product  being  carbonic-oxide  gas,  CO. 

Q.  What  are  the  ordinary  combinations  of  hydrogen 
with  carbon  fuel? 

Hydrogen  is  rarely  found  in  a  free  state,  though  it  is 
an  essential  element  in  all  organic  substances,  from  which 
it  may  be  separated  by  a  process  of  destructive  distilla- 
tion. It  occurs  in  nature  in  combination  with  carbon. 
The  compound  which  contains  it  in  greatest  abundance  is 
marsh  gas,  of  which  hydrogen  forms  one-fourth,  CH4. 
Olefiant  gas  consists  of  2,  atoms  of  carbon  and  4  atoms  of 
hydrogen,  C2H4.  These  are  the  commonest  proportions 
in  which  the  two  elements,  hydrogen  and  carbon,  are 
found  in  coal.  The  complete  series,  however,  of  hydro- 
carbons is  so  extended  that  it  cannot  be  reproduced  here. 
Reference  can  only  be  made  to  the  Marsh  gas  and  Olefiant 
gas  series,  which  are  given  elsewhere  in  this  volume. 

Q.  Is  oxygen  a  supporter  of  combustion  ? 

Oxygen  is  an  active  supporter  of  combustion.  It  will 
unite  chemically  with  the  hydrogen  and  the  carbon  in  the 
fuel,  the  burning  of  the  latter  accompanied  by  characteris- 
tic flames  followed  by  a  body  of  incandescent  carbon  on 
the  grate,  which  will  continue  to  burn  at  high  temperature 
and  with  great  brilliancy,  until  entirely  consumed,  if  a 
proper  supply  of  atmospheric  oxygen  is  furnished. 

Oxygen  will  not  unite  with  hydrogen  and  carbon  at 
ordinary  temperatures.  A  mixture  of  oxygen  and  hydro- 
gen may  be  thus  kept  for  any  length  of  time,  but  if  the 


86  COMBUSTION   OF   COAL. 

temperature  of  any  part  of  the  mixture  be  raised  to  bright 
redness — either  by  an  electric  spark,  by  the  presentation 
of  a  flame,  or  by  other  means — ignition  at  once  takes 
place  with  explosive  force  throughout  the  whole  mass. 

Q.  How  may  the  volume  of  oxygen  required  for  com- 
bustion be  estimated  ? 

By  weight,  air  consists  of  23  per  cent  of  oxygen  and  77 
per  cent  of  nitrogen;  therefore,  77-^-23  =  3.391  pounds  of 
nitrogen  accompanies  each  pound  of  oxygen. 

By  volume,  one  pound  of  air  averages  12.5  cubic  feet, 
of  which  21  per  cent,  or  2.625  cubic  feet,  is  oxygen,  and 
79  per  cent,  or  9. 875  cubic  feet,  is  nitrogen. 

One  pound  of  carbon  requires  for  its  complete  combus- 
tion to  CO2  about  12  pounds  of  air,  or  150  cubic  feet,  of 
which  21  per  cent,  or  31.5  cubic  feet,  is  oxygen,  and  79 
per  cent,  or  118.5  cubic  feet,  is  nitrogen. 

One  pound  of  hydrogen  requires  for  its  complete  com- 
bustion to  H2O  8  pounds  of  oxygen  supplied  by  3 1  pounds 
of  air,  or  387.5  cubic  feet,  of  which  21  per  cent,  or  81.375 
cubic  feet,  is  oxygen,  and  79  per  cent,  or  306.125  cubic 
feet,  is  nitrogen. 

Q.  What  is  meant  by  the  term  ignition  ? 

Ignition  is  simply  the  incandescence  of  a  body  unat- 
tended by  chemical  change,  and  must  not  be  confused 
with  combustion.  The  ignition  of  solids  is  a  source  of 
light,  the  combustion  of  solids  is  a  source  of  heat.  Every 
combustible  must  be  heated  to  a  certain  definite  temper- 
ature before  it  will  combine  with  oxygen.  This  temper- 
ature is  usually  called  the  point  of  ignition,  or  its  kindling 
temperature.  In  furnace  combustion  the  temperature  of 
ignition  cannot  be  much  less  than  dull  red  heat,  say  800° 


IGNITION    TEMPERATURE    OF    GASES.  8/ 

to  900°  F.,  and  maintain  an  active  fire.  For  steam-boiler 
furnaces  the  combustion  is  quite  active,  even  for  moderate 
fires,  and  the  temperature  of  the  incandescent  bed  of  fuel 
seldom  if  ever  below  1100°  to  1200°  F.  and  usually  much 
higher  than  that,  while  the  full  furnace  temperature  may 
range  from  2000°  to  3000°  F. 

Q.  What  are  the  ignition  temperatures  of  gases  ? 

We  have  as  yet  no  very  exact  information  concerning 
the  ignition  temperatures  of  gases.  The  experimental 
difficulties  in  the  way  of  carrying  out  such  determinations 
are  very  considerable.  It  is,  however,  certain  that  the 
ignition  temperatures  of  gaseous  mixtures  are  as  a  rule  by 
no  means  so  high  as  is  commonly  supposed,  and  they  lie 
within  extremes  of  temperature  admitting  of  comparative- 
ly easy  determination.  When  once  initiated,  the  continu- 
ance of  the  combination  of  unlimited  amounts  of  the  con- 
stituents of  a  combustible  mixture,  or,  in  other  words,  the 
continued  existence  of  a  flame,  depends  primarily  upon  the 
condition  that  the  combining  gases  are  maintained  at  the 
temperature  required  to  bring  about  their  union.  Any 
agency  or  condition  which  lowers  the  temperature  below 
this  point  will  extinguish  the  flame. 

Q.  What  is  the  effect  upon  combustion  if  too  little  air 
is  supplied  the  fire  ? 

So  far  as  the  carbon  of  the  fuel  is  concerned  the  effect 
is  a  serious  one.  One  pound  of  carbon  combining  with 
two  pounds  of  oxygen  results  in  perfect  combustion,  the 
product  being  carbonic-acid  gas,  CO2,  developing  14,500 
heat  units;  but  if  too  little  air,  which  means  too  little 
oxygen,  is  present  at  the  instant  and  focus  of  combustion, 
the  carbonic-acid  gas  already  formed  will  take  up  addi- 


88  COMBUSTION    OF   COAL. 

tional  carbon,  thus  changing  the  product  to  carbonic 
oxide,  or  from  CO2  to  CO,  the  latter  developing  only  4,450 
heat  units,  or  10,050  less  than  the  first  union.  This 
represents  a  loss  approximating  69  per  cent  of  the  fuel, 
merely  as  a  result  of  too  little  air  in  the  fire  at  the  right 
time  and  place. 

Q.  What  is  the  effect  upon  combustion  if  too  much  air 
is  supplied  the  fire  ? 

The  effect  of  too  much  air  in  the  fire  is  the  mechanical 
one  of  cooling  the  furnace.  The  carbon  having  united 
with  its  full  combining  weight  of  oxygen  to  form  CO.,  can 
take  up  no  more  oxygen,  and  any  surplus  air  in  the  furnace 
is  merely  a  dilutant  of  the  gases.  Inasmuch  as  the  free 
air  abstracts  heat  from  the  furnace  and  does  no  useful 
work,  its  presence  acts  against  the  economy  of  the  furnace. 

Q.  Does  so  large  an  excess  of  air  as  150  per  cent  over 
that  necessary  for  complete  combustion  commonly  occur 
in  steam  boiler  furnaces? 

An  excess  of  air  as  large  as  150  per  cent  in  steam-boiler 
furnaces  is  by  no  means  uncommon.  There  is  a  general 
tendency  to  use  a  stronger  draught  than  is  necessary  for 
the  combustion  of  fuel.  It  so  happens  that  100  per  cent 
excess  of  air  in  steam-boiler  furnaces  is  an  ordinary  condi- 
tion, and  1 50  per  cent  excess  is  much  more  common  than 
is  generally  supposed. 

Q.  What  advantages  accompany  the  heating  of  air  re- 
quired for  furnace  combustion? 

A  direct  economical  effect  of  heating  the  air  is  that  of 
raising  the  intensity  of  furnace  combustion,  and  this  may 
be  explained  on  the  probable  hypothesis  that  the  chemical 


HEATED   AIR   AND    CHEMICAL   ACTION.  89 

affinity  of  heated  air  for  carbon  is  much  greater  than  that 
of  cold  air  ;  one  consequence  of  which  is  that,  when  heated 
air  is  employed,  it  is  deprived  of  its  oxygen  within  a  very 
short  travel,  the  combustion  is  thereby  more  concentrated 
and  localized  at  the  focus  where  the  heat  has  to  be  applied 
and  to  do  its  work.  This  is  favorable  to  the  economy  of 
fuel,  for  combustion  and  high  temperature  beyond  the 
point  where  heat  has  to  be  applied  are  useless. 

Q.  How  may  the  effect  of  heated  air  and  chemical 
action  be  estimated  ? 

It  is  known  that  one  pound  of  carbon  combined  with  2\ 
pounds  of  oxygen  will  develop  14,500  heat  units.  This 
will  require  under  theoretical  conditions  12  pounds  of  air; 
but  to  place  it  under  ordinary  conditions,  say  24  pounds 
of  air.  We  have  then  25  pounds  of  gaseous  product,  of 
which  3^|  pounds  will  be  carbonic-acid  gas,  and  21^ 
pounds  of  inert  waste  gas.  The  more  nitrogen  there  hap- 
pens to  be  mingled  with  the  oxygen,  the  greater  the 
weight  of  matter  that  will  have  to  be  uselessly  heated; 
and  the  greater  its  capacity  for  absorbing  heat  —  the 
greater  its  specific  heat  —  the  greater  the  amount  of  heat 
that  would  be  taken  up. 

The  specific  heat  of  carbonic  acid  gas  =  o.  2  1  7,  of  nitro- 
gen =  o.  245.  The  mean  of  3f  pounds  of  the  first  and  2  i-J- 


pounds  of  the  latter  =  0.237.     Then  :  _    i-_  =2,447° 

0.237  X  25 

F.  as  the  temperature  of  the  products  of  combustion,  in 
the  form  of  about  1,800  cubic  feet  of  fire  gases. 

Preheating  the  air  facilitates  the  union  of  oxygen  with 
the  carbon,  and  the  fourfold  useless  volume  of  nitrogen 
should  not  rob  the  furnace  of  heat  at  the  very  moment  and 
focus  of  its  combustion.  A  gain  would  also  be  effected 


90  COMBUSTION   OF   COAL. 

the  more  nearly  the  temperature  of  the  nitrogen  is  raised 
to  that  of  the  fire ;  and  whatever  can  be  done  by  means  of 
the  escaping  gases  is  pure  saving. 

Q.  Is  there  an  economical  limit  to  the  heating  of  air 
for  combustion  ? 

It  has  been  found  in  practice  that  the  greater  the  affinity 
of  any  fuel  for  oxygen,  the  lower  need  be  the  temperature 
of  the  air.  It  is  hence  used  at  a  lower  heat  in  charcoal 
furnaces  than  in  coke  furnaces,  and  less  in  the  latter  than 
in  anthracite  blast  furnaces.  This  explains  the  fact, 
which  has  been  found  on  trial,  that  a  reverbatory  furnace, 
supplied  with  hot  air  at  the  grate  only,  has  actually  been 
found  to  have  its  efficiency  diminished  and  not  increased. 
The  gaseous  combination  or  chemical  union  being  thereby 
accelerated,  the  combustion  takes  place  more  on  the  grate 
and  less  in  the  body  of  the  furnace,  where  the  actual  work 
has  to  be  done. 

Q.  What  is  flame? 

Flame  is  the  surface  burning  of  an  inflammable  gas  or 
vapor,  the  surface  of  which  is  in  contact  with  or  receives 
constant  supplies  of  atmospheric  air.  As  all  flames  de- 
pending upon  oxygen  for  their  support  are  specifically 
lighter  than  air,  they  naturally  ascend  in  a  stream  from 
burning  bodies.  Flames  are  usually,  though  not  neces- 
sarily, accompanied  by  luminosity  at  ordinary  atmos- 
pheric pressure. 

Q.  What  is  known  regarding  the  nature  of  the  chemical 
processes  in  flames? 

Attempts  have  been  made  to  study  the  nature  of  the 
chemical  processes  in  flames  of  candles  and  of  coal  gas  by 
aspirating  the  gases  from  different  parts  of  the  flame  and 


STRUCTURE   OF   FLAME.  9! 

analyzing  them.  Such  investigations  can  only  give  a  very 
partial  conception  of  the  changes  which  occur,  or  have 
occurred,  in  the  different  areas  of  the  flame,  owing  to  the 
intense  molecular  movements,  due  to  the  high  temperature 
and  specific  differences  of  diffusive  power  of  the  gaseous 
constituents.  Nevertheless  it  is  possible  to  obtain  some 
idea  of  the  manner  in  which  the  several  combustible  gases 
in  such  a  complex  mixture  as  that  of  coal  gas,  or  of  the 
gas  obtained  by  the  distillation  of  wax  or  tallow,  behave 
toward  oxygen,  and  to  trace  the  rates  at  which  they  are 
severally  burnt.  Thus,  broadly  speaking,  it  is  found  that 
of  these  gases,  the  hydrogen  up  to  a  certain  point  is  most 
rapidly  consumed,  then  the  carbonic  oxide,  next  the  marsh 
gas,  while  the  heavy  hydrocarbons  burn  comparatively 
slowly.  The  amounts  of  these  gases  burnt,  and  especially 
of  the  hydrogen  and  carbonic  oxide,  are,  however,  modified 
by  processes  of  dissociation  and  by  the  mutual  action  of 
the  products  of  combustion  at  high  temperatures.  At  the 
very  high  temperatures  water  vapor  and  carbonic-acid  gas 
are  dissociated,  while  carbonic  oxide  is  formed  by  the 
action  of  separated  carbon  upon  carbonic-acid  gas. 

Q.  How  is  an  isolated  flame  such  as  a  candle  built  up  ? 

It  is  usual  to  describe  the  structure  of  a  flame  as  built 
up  of  four  zones,  as  sketched  in  Fig.  i,  intended  to  illus- 
trate the  main  reaction  taking  place  in  the  flame  of  a 
burning  candle,  in  which  : 

A  —  the  inner  zone  of  heavy  vapor. 

B  =  the  inner  zone  of  lighter  gas. 

C  =  the  luminous  zone. 

D  =  the  outer  or  cooling  zone. 

The  inner  zone  A,  nearest  to  and  surrounding  the  wick, 
is  a  vapor  of  the  material  of  which  the  candle  is  composed. 


92 


COMBUSTION   OF   COAL. 


The  zone  B  is  an  envelope  of  highly  rarified  vapor  of  A 
heated  to  the  point  of  ignition.  The  zone  C  is  luminous, 
and  is  that  portion  of  the  flame 
where  the  chemical  reactions  occur, 
beginning  along  the  surface  of  the 
zone  B  and  extending  into  the  zone 
D.  The  outer  zone  D  is  that  in 
which  the  cooling  and  diluting  in- 
fluence of  the  entering  air  renders  a 
thin  layer  non-luminous,  and  finally 
extinguishes  it. 

It  will  be  -understood  that  flame 
does  not  consist  of  envelopes  in  such 
contrast  as  the  engraving  would  seem 
to  indicate.  This  is  for  the  purpose 
of  illustration  only. 

Q.  What  are  the  successive  devel- 
opments of  a  luminous  hydrocarbon 
flame? 


FIG. 


The  hydrocarbon  issues  from  the 
wick  of  the  candle,  Fig.  i,  let  us 
suppose  as  a  cylindrical  column.  This  column  is  not 
sharply  marked  off  from  the  air,  but  is  so  penetrated 
by  the  latter  that  we  must  suppose  a  gradual  transition 
from  the  pure  hydrocarbon  in  the  centre  of  the  column 
to  the  pure  air  outside.  Take  a  thin,  transverse  slice 
of  the  flame,  near  the  lower  part  of  the  wick.  At 
what  lateral  distance  from  the  centre  will  combustion  be- 
gin? Clearly  where  enough  oxygen  has  penetrated  the 
column  to  give  such  partial  combustion  as  takes  place  in 
the  inner  cone  of  a  Bunsen  burner.  This,  then,  defines 
the  blue  region. 


STRUCTURE   OF   FLAME.  93 

Outside  this,  the  combustion  of  the  carbonic  oxide, 
hydrogen,  and  any  hydrocarbons  which  pass  from  the  blue 
region  takes  place,  and  constitutes  the  faintly  luminous 
region. 

These  two  layers  form  a  sheath  of  active  combustion, 
surrounding  and  intensely  heating  the  hydrocarbons  in  the 
central  parts  of  the  column.  These  heated  hydrocarbons 
rise,  and  are  heated  to  a  higher  temperature  as  they  as- 
cend. They  are  accordingly  decomposed  with  the  separa- 
tion of  carbon  in  the  higher  parts  of  the  flame,  giving  us 
the  yellow  region ;  but  there  remains  a  central  cone  in 
which  neither  is  there  any  oxygen  for  combustion  nor  a 
sufficiently  high  temperature  for  decomposition.  This 
constitutes  the  dark  region  of  tinburned  gases. 

A  flame  is,  however,  not  cylindrical,  but  has  in  the  case 
of  a  candle  an  inverted  peg-top  shape.  Again,  the  blue 
region  only  surrounds  the  lower  part  of  the  flame,  while 
the  faintly  luminous  part  surrounds  the  whole. 

Q.  How  will  the  processes  outlined  in  the  above  question 
differ  in  parts  above  the  small  section  of  the  flame  ? 

Let  us  suppose  that  the  changes  have  gone  on  in  the 
small  section  of  the  flame  exactly  as  described  above. 
The  central  cone  of  unburned  gases  will  pass  up- 
ward, and  may  be  treated  as  a  new  cylindrical  column, 
which  will  undergo  changes  just  as  the  original  one,  leav- 
ing, however,  a  smaller  cone  of  unburned  gases;  or,  in 
other  words,  each  succeeding  section  of  the  flame  will  be 
of  smaller  diameter.  This  is  what  gives  the  conical  struc- 
ture to  the  flame.  Again,  the  higher  we  go  in  the  flame, 
the  greater  proportionally  is  the  amount  of  separated  car- 
bon, for  we  have  not  only  the  heat  of  laterally  outlying 
combustion  to  affect  decomposition,  but  also  that  of  the 


94  COMBUSTION   OF   COAL. 

lower  parts  of  the  flame.  The  lower  part  of  a  luminous 
flame  is  accordingly  cooler,  and  contains  less  separated 
carbon  than  the  upper. 

Q.  What  chemical  changes  produce  the  blue  region  in 
a  flame  ? 

When  the  hydrocarbons  are  cool  until  admixed  with 
sufficient  air  for  combustion,  in  the  lower  part  of  the 
flame,  there  is  every  facility  for  the  occurrence  of  the 
chemical  changes  to  which  the  existence  of  the  blue  re- 
gion has  been  ascribed,  and  the  blue  region  here  is  most 
evident;  whereas  in  the  upper  parts  of  the  flame,  where 
the  quantity  of  hydrocarbon  decomposed  (with  separation 
of  carbon)  by  heat  is  relatively  much  greater,  there  is  not 
enough  left  to  form  outside  the  yellow  part  the  mixture  to 
which  the  blue  region  of  flame  is  due.  The  blue  region, 
therefore,  rapidly  thins  off  as  we  ascend  the  flame. 

Q.  Are  the  several  processes  of  flame  development  sup- 
ported by  complete  combustion  ? 

Whether  the  first  combustion  taking  place  within  the 
flame  is  that  of  undecomposed  hydrocarbon  with  limited 
oxygen,  or  of  the  decomposed  hydrocarbon  with  limited 
oxygen,  we  may  be  sure  that  the  products  will  contain 
carbonic  oxide,  and  perhaps  hydrogen  ;  and  we  shall  there- 
fore have  all  round  tJie  flame  a  faintly  luminous  region  of 
completed  combustion. 

Q.  Is  the  flame  of  a  candle  characteristic  of  other  steady 
or  continuous  flames? 

In  other  steady,  continuous  flames  these  areas  or  zones, 
as  shown  in  the  candle,  are  very  different  in  character  and 
in  number.  In  some  the  luminous  cone  is  absent,  and 
others  have  no  mantle.  All  have,  of  course,  the  dark  in- 


RATE  OF  PROPAGATION  IN  FLAME.        95 

ternal  cone,  and  the  majority  have  an  area  corresponding 
to  the  blue  zone  in  the  candle  flame.  The  flame  of  car- 
bonic oxide  consists  of  a  dark  internal  cone  of  unburnt 
gas  surrounded  by  a  yellowish-red  mantle,  somewhat  ill- 
defined  at  its  external  edge,  and  at  the  base  is  a  compara- 
tively large  blue  zone. 

Q.  How  can  it  be  shown  that  the  flame  of  a  candle  is 
hollow  ? 

The  fact  that  the  candle  flame  is  hollow,  and  that  the 
internal  cone  immediately  surrounding  the  wick  consists 
of  comparatively  cold,  unignited  gas  free  from  oxygen, 
may  be  demonstrated  by  thrusting  a  fragment  of  burning 
phosphorus  into  the  cone  when  its  combustion  ceases. 

A  piece  of  stiff  thick  paper  thrust  down  on  the  flame  to 
the  level  of  the  dark  internal  area  is  seen  to  be  charred 
on  the  upper  surface  in  the  form  of  a  ring.  If  the  paper 
be  placed  simply  across  the  luminous  area  and  above  the 
dark  cone,  the  charring  is  simply  a  circular  patch. 

Q.  What  is  the  rate  of  propagation  of  combustion  in 
flames  of  hydrogen  and  carbonic  oxide? 

Bunsen's  investigations  show  that  the  rate  of  propaga- 
tion of  the  combustion  of  a  mixture  of  oxygen  and  hydro- 
gen, and  of  carbonic  oxide  and  oxygen,  mixed  in  the  exact 
quantities  for  complete  combustion  to  be : 

In  the  oxyhydrogen  mixture  the  velocity  of  the  inflam- 
mation was  111.5  feet  per  second;  in  that  of  carbonic 
oxide  and  oxygen  it  was  less  than  40  inches  per  second. 
By  adding  to  the  mixture  increasing  amounts  of  an  indif- 
ferent gas  the  rate  is  rapidly  diminished  until  the  progress 
of  the  flame  throughout  the  mass  may  be  followed  with 
the  eye. 


g6  COMBUSTION   OP'   COAL. 

Q.  Is  combustion  complete  and  the  consequent  high 
flame  temperature  maintained  in  cases  where  the  combus- 
tible gases  are  mixed  in  their  exact  combining  propor- 
tions ? 

According  to  Bunsen,  in  a  mixture  of  carbonic  oxide, 
CO,  or  hydrogen,  with  oxygen  in  the  exact  quantity 
needed  for  complete  combination,  only  one-third  of  the 
carbonic  oxide,  CO,  or  hydrogen,  is  burnt  at  the  maximum 
temperature,  the  remaining  two-thirds  at  the  high  tem- 
perature (2558°-3O33°)  having  lost  the  power  of  combina- 
tion. If  an  indifferent  gas  is  present  the  temperature  of 
the  flame  is  reduced,  and  larger  quantities  of  the  gases 
combine  together,  as  much  as  half  the  amount  of  carbonic 
oxide,  CO,  or  hydrogen  combining  within  a  range  of  tem- 
perature between  2471°  and  1 146°. 

It  would  appear  therefore  that  gases  in  combining  to- 
gether with  the  production  of  such  an  amount  of  heat  as 
to  produce  flame  unite,  as  it  were,  at  a  single  leap,  and 
that  the  combustion  is  not  a  continuous  uninterrupted 
process. 

Q.  What  variations  of  temperature  occur  in  flames  in- 
cident to  the  combustion  of  carbonic  oxide,  CO? 

When  two  volumes  of  carbonic  oxide,  CO,  are  mixed 
with  one  volume  of  oxygen,  both  gases  at  o°,  and  the 
mixture  is  ignited,  the  temperature  is  raised  to  3033°,  and 
two-thirds  of  the  CO  is  left  unburnt.  By  radiation  and 
conduction  the  temperature  is  lowered  to  2558°  without 
any  combustion  of  the  CO.  At  a  little  below  this  point 
combustion  recommences,  and  the  temperature  is  again 
raised  to  2558°,  but  not  above  this  point.  This  temper- 
ature continues  until  half  the  CO  is  burnt,  when  combus- 
tion ceases,  until  by  cooling  and  radiation  the  gaseous 


LUMINOSITY    OF   FLAME.  97 

mixture  has  cooled  to  1146°;  and  these  alternate  phases 
of  constant  temperature  and  of  decreasing  temperature  are 
repeated  until  the  whole  of  the  combustible  gas  is  burnt. 

Q.  What  is  the  cause  of  the  luminosity  of  flame? 

The  main  cause  of  the  luminosity  of  flame  was  first 
traced  by  Davy  as  the  outcome  of  experiments  which  led 
him  to  the  invention  of  the  safety  lamp.  It  is,  to  use  his 
own  words,  "  owing  to  the  decomposition  of  a  part  of  a  gas 
toward  the  interior  of  the  flame,  where  the  air  was  in 
smallest  quantity,  and  the  decomposition  of  solid  charcoal, 
which  first  by  its  ignition  and  afterward  by  its  combustion 
increases  in  a  high  degree  the  intensity  of  the  light." 

The  proofs  that  solid  carbon  is  present  in  luminous 
hydrocarbon  flames  are  the  following : 

1.  Chlorine  causes   an    increase    in  the  luminosity  of 
feebly    luminous    or    non-luminous    hydrocarbon    flames. 
Since  chlorine  decomposes  hydrocarbons  at  a  red  heat  with 
separation  of  carbon,  it  follows  that  the  increase  in  lumin- 
osity is  due  to  the  production  of  solid  carbon  particles. 

2.  A  rod  held    in  the  luminous   flame  soon  becomes 
covered  on  its  lower  surface,  i.e.,  the  surface  opposed  to 
the  issuing  gas,  with  a  deposit  of  soot.     The  solid  soot  is 
driven  against  the  rod.     If  the  soot  existed  as  vapor  within 
the  luminous  flame,  its  deposition  would  be  due  to  a  dimi- 
nution of  the  temperature  of  the  flame,  and  would  there- 
fore occur  on  all  sides  of  the  rod. 

3.  A  strongly  heated  surface  also  becomes  covered  with 
a  deposit  of  soot.      This  result  could  not  occur  if  the  de- 
posit were  due  to  the  cooling  action  of  the  surface. 

4.  The  carbon  particles  in  the  luminous  flame  are  ren- 
dered visible  when  the  flame  comes  in  contact  with  an- 
other flame,  or  with  a  heated  surface.     The  separated  par- 

7 


98  COMBUSTION   OF   COAL. 

tides  are  agglomerated  into  large  masses,  and  the  luminous 
mantle  becomes  rilled  with  a  number  of  glowing  points, 
giving  a  very  coarse  grained  soot. 

5.  The  transparency  of  a  luminous  flame  is  no  greater 
than  that  of  the  approximately  equally  thick  stratum  of 
soot  which  rises  from  the  flame  of  burning  turpentine,  and 
which  is  generally  allowed  to  contain  solid  particles.     A 
flame   of    hydrogen    made  luminous  with    solid    chromic 
oxide,  which  is  non-volatile,  is  as  transparent  as  the  hy- 
drocarbon flame. 

6.  Flames  which  undoubtedly  owe  their  luminosity  to 
finely  divided  solid  matter  produce  shadows  in  sunlight. 
The  only  luminous  flames  incapable  of  producing  shadows 
are  those  consisting  of  glowing  gases  and  vapors. 

7.  Luminous     hydrocarbon    flames    produce    strongly 
marked  shadows    in    sunlight.     These  flames,   therefore, 
contain  finely  divided    solid   matter.     This   solid  matter 
must  be  carbon,  since  no  other  substance  capable  of  re- 
maining solid  at  the  temperature  of  these  flames  is  present. 
Moreover,  if  the  soot   in   luminous   flames   is  present  as 
vapor,  a  high  temperature  after  condensation  should  again 
cause  it  to  assume  the  gaseous  condition ;  but  soot  is  ab- 
solutely non- volatile,  even  at  the  highest  temperatures. 

Q.  What  conditions  affect  the  color  of  flame  ? 

The  conditions  under  which  a  flame  is  produced  not  only 
modify  its  temperature,  but  also,  as  an  effect  of  temper- 
ature, its  color.  Thus  the  prevailing  tint  of  sulphur  burn- 
ing in  air  is  blue,  and  the  mantle  is  correspondingly  small 
and  of  a  violet  color.  In  oxygen  the  flame  becomes  hotter 
and  the  violet  color  is  more  pronounced.  Precisely  the 
same  change  is  produced  by  heating  the  air  or  by  burning 
a  jet  of  heated  sulphur  vapor.  Cold  carbonic  oxide  gives 


TEMPERATURE    OF   FLAME.  99 

a  blue  flame  in  air,  but  it  becomes  yellowish-red  if  the  gas 
be  previously  heated. 

The  flame  of  a  candle,  whether  of  wax,  tallow,  or  para- 
fin,  is  seen  to  consist  of  four  distinct  cones,  which  are 
comparatively  sharply  defined,  and  which  are  rendered  evi- 
dent by  their  different  appearance.  Immediately  surround- 
ing the  wick  is  a  dark  inner  cone  of  unburnt  gases  or  vap- 
ors. Adjoining  the  inner  cone  is  a  light  blue  zone  of 
small  area  consisting  of  combustible  matter  from  the  wick. 
Surrounding  the  inner  cone  is  a  bright  luminous  area,  from 
which  the  greater  part  of  the  light  emitted  by  the  flame  is 
derived.  Surrounding  the  luminous  area,  which  seems  to 
constitute  the  greater  portion  of  the  visible  flame,  is  an 
envelope  or  mantle  of  a  faint  yellowish  color  and  of  feeble 
luminosity.  This  consists  of  the  final  products  of  combus- 
tion of  the  constituents  of  the  luminous  cone  mixed  with 
atmospheric  air  heated  to  incandescence. 

Owing  to  the  intense  glare  of  the  luminous  cone  the 
feebly  luminous  mantle  is  hot  readily  perceived,  but  it 
may  be  rendered  evident  by  holding  a  piece  of  card,  of  the 
shape  of  the  flame,  in  such  a  manner  as  to  hide  the  lumi- 
nous cone,  when  the  mantle  is  seen  lining  the  outer  edge 
of  the  cone. 

Q.  Upon  what  does  the  temperature  of  flame  depend? 

The  temperature  of  a  flame  depends  mainly  upon  the 
heats  of  combination  of  the  constituents  and  the  specific 
heats  of  the  products  of  combustion.  Flames  which  de- 
pend upon  the  presence  of  oxygen  are  much  hotter  when 
the  combustion  takes  place  in  an  atmosphere  of  pure  gas 
than  in  air.  In  the  latter  case  the  oxygen  is  mixed  with 
four  times  its  volume  of  nitrogen,  which  plays  no  part  in 
the  chemical  reaction,  and  therefore  contributes  nothing 


100  COMBUSTION   OF   COAL. 

to  the  heating  effect ;  but,  on  the  contrary,  abstracts  a 
considerable  amount  of  heat  from  the  products  of  combus- 
tion, and  thereby  lowers  the  temperature  of  the  glowing 
mass  of  gas.  Hence  sulphur  burning  in  oxygen  gives  a 
much  hotter  flame  than  when  burning  in  air,  and  the  oxy- 
hydrogen  flame  is  much  hotter  than  that  of  hydrogen  in 
air.  "  The  effect  of  the  indifferent  gas  in  lowering  the 
temperature  is  well  illustrated  by  the  following  numbers 
given  by  Bunsen : 

Cent.  Fahr. 

Flame  of  hydrogen  burning  in  air 2,024°  3.675° 

"       "         "  "        "oxygen 2,844  S^S1 

"       "  carbonic  oxide  burning  in  air J.997  3,626 

"      "         "         "  "        "  oxygen....  3,003  5,437 

Q.  Is  flame  in  immediate  contact  with  the  orifice,  from 
which  the  gas  issues? 

If  the  flame  of  a  candle  or  of  coal  gas  be  closely  ex- 
amined it  will  be  seen  that  the  one  does  not  touch  the  rim 
of  the  burner  nor  the  other  the  wick.  The  intermediate 
space  in  the  case  of  the  coal  gas  may  be  increased  by  mix- 
ing it  with  an  indifferent  gas,  as  nitrogen  or  carbonic-acid 
gas,  CO2.  These  phenomena  are  due  to  the  cooling  effect 
of  the  wick  or  the  burner. 

Q.  May  flame  be  extinguished  by  a  rapid  absorption 
of  its  heat? 

A  coal  gas  flame  may  be  extinguished  by  a  cold  mass 
of  copper,  and  a  candle  flame  by  a  helix  of  cold  copper 
wire.  The  metal  abstracts  sufficient  heat  from  the  gases 
to  lower  their  temperature  below  the  point  of  combination. 
If  the  metal  is  heated  prior  to  its  introduction  into  the 
flames,  they  are  not  extinguished. 


FLAME    OF   ANTHRACITE    COAL.  TOT 

Q.  May  not  a  flame  be  extinguished  in  other  ways 
than  by  the  cooling  action  of  metals  ? 

A  flame  may  be  extinguished  by  mixing  the  combustible 
gases  with  a  sufficiently  large  quantity  of  an  indifferent 
gas,  which  will  act  by  absorption  of  heat  in  the  same  way 
as  metal.  The  effect  even  of  small  quantities  of  indiffer- 
ent or  chemically  inactive  gases  in  lowering  the  temper- 
ature of  a  flame  is  very  marked,  and  is  well  illustrated  in 
the  different  characters  of  the  flame  of  hydrogen  burning 
in  air  and  oxygen.  In  extinguishing  a  flame,  say  of  a 
candle  or  coal  gas,  by  blowing  it  out,  the  puff  of  air  acts 
partly  by  suddenly  scattering  the  glowing  gases  from  the 
area  of  supply  and  partly  by  its  cooling  action. 

Q.  What  are  the  flame  characteristics  in  the  burning 
of  anthracite  coal? 

In  burning,  anthracite  coal  neither  softens  nor  swells, 
and  does  not  give  off  smoke.  The  flame  is  quite  short 
and  has  a  yellowish  tinge  when  first  thrown  upon  the  fire, 
which  soon  changes  to  a  faint  blue,  with  occasionally  a 
red  tinge.  The  flame,  being  quite  short  and  free  from 
particles  of  solid  carbon,  has  the  .appearance  of  being 
transparent. 

Q.  How  is  the  rapidity  of  flow,  or  the  volume  of  air 
supplied  a  furnace-fire,  estimated,  when  employing  natural 
draft  ? 

By  means  of  an  instrument  contrived  for  measuring  the 
force  and  velocity  of  currents  of  air,  called  an  anemometer. 
Those  composed  of  a  small  light  fan  wheel,  whose  motion 
is  transmitted  to  a  counter  which  registers  the  number  of 
turns,  are  most  certain  and  convenient  for  use,  though 
they  must  previously  be  tested,  or  the  relation  existing 


IO2  COMBUSTION    OF   COAL. 

between  the  velocity  of  the  wind  and  the  number  of  turns 
of  the  wings  must  be  accurately  determined. 

The  anemometer  shown  in  Fig.  2  is  by  Keuffel  &  Esser 
Company,  New  York.     Each  instrument  is  tested  and  a 


FIG,  2. 


chart  of  corrections  furnished  with  it,  so  that  no  calcula- 
tions are  necessary  for  obtaining  the  velocity  of  the  cur- 
rent in  which  it  is  placed. 


CHAPTER  V. 

PRODUCTS    OF   COMBUSTION. 

Q.  What  are  the  principal  products  in  the  furnace  after 
the  combustion  of  coal  ? 

The  principal  products  in  the  furnace  after  the  combus- 
tion of  coal  are :  carbonic-acid  gas,  carbonic  oxide,  nitro- 
gen, air  furnished  in  excess,  and  unconsumed,  gaseous 
steam. 

Q.  What  is  the  product  of  the  combustion  of  hydrogen  ? 

Hydrogen  unites  with  oxygen,  forming  gaseous  steam, 
which,  upon  cooling,  is  condensed  into  water,  H2O.  This 
chemical  combination  is  complete,  and  the  product  incom- 
bustible. 

Q.  What  are  the  products  of  the  combustion  of  carbon  ? 

The  products  of  the  combustion  of  carbon  in  oxygen  are 
two  in  number,  carbonic  oxide,  CO,  and  carbonic-acid  gas, 
COy,  in  which  each  compound  is  sharply  defined  and  ex- 
hibits properties  distinct  from  each  other,  and  of  the  ele- 
ments of  which  they  are  composed.  The  quantity  of 
carbon  remaining  the  same,  the  quantity  of  oxygen  must 
be  doubled  in  order  to  form  the  other  compound.  These 
proportions  constitute  the  only  two  direct  inorganic  com- 
pounds of  carbon  and  oxygen. 


104  COMBUSTION   OF   COAL. 

Q.  What  are  the  properties  of  carbonic-acid  gas? 

Carbonic-acid  gas,  CO,,  is  composed  of  one  part  or 
atom  of  carbon  and  two  parts  of  oxygen,  its  atomic  weight 
being  12  +  (16  X  2)  —  44.  By  percentage  of  volume: 
carbon  =  27.27,  oxygen  =  72.73  =  100.00.  Its  specific 
gravity  is  1.53,  air  =  i.oo.  It  is  a  colorless,  inodorous, 
heavy  gas,  neither  combustible  nor  a  supporter  of  combus- 
tion. 

It  liquefies  under  a  pressure  of  36  atmospheres  at  o°  C. 
The  specific  gravity  of  the  liquid  carbonic  acid  is  1.057  at 
-  34°  C.  Liquid  carbonic  acid  is  colorless,  very  soluble 
in  alcohol,  ether,  and  volatile  oils,  but  does  not  mix  with 
water.  When  the  pressure  is  suddenly  relieved,  part  of 
the  carbonic  acid  immediately  vaporizes,  producing  suffic- 
ient cold  to  solidify  the  remainder.  Solid  carbonic  acid  is 
a  white  flocculent,  snowlike  mass,  and  may  be  left  exposed 
to  the  air  for  some  time  without  sensible  evaporation.  An 
air  or  spirit  thermometer  immersed  in  it  sinks  10  —  78°  C. 
It  can,  however,  be  placed  on  the  hand  without  any  acute 
sensation  of  cold.  By  mixing  with  ether  its  refrigerating 
power  is  greatly  increased.  The  cold  produced  in  this 
manner  is  sufficient  to  solidify  mercury  and  to  liquefy 
several  gases. 

Carbonic-acid  gas  is  a  constant  constituent  of  the  atmos- 
phere, which  contains  on  an  average  about  o.  034  per  cent. 

In  the  combustion  of  coal,  carbonic-acid  gas  is  formed 
by  the  combination  of  the  carbon  in  the  coal  by  the  oxy- 
gen of  the  air,  and  is  thus  a  constant  product  of  the  ordi- 
nary processes  of  combustion.  The  presence  of  moisture 
is  necessary  for  the  burning  of  carbon  in  an  atmosphere  of 
pure  oxygen.  In  furnace  combustion  the  coal  itself  fur- 
nishes all  the  moisture  needed  for  intense  combustion. 


CARBONIC    OXIDE.  10$ 

Q.  What  are  the  properties  of  carbonic  oxide  ? 

Carbonic  oxide,  CO,  is  composed  of  one  part  or  atom 
each  of  carbon  and  oxygen,  its  atomic  weight  being  12  -|- 
16  =  28.  By  percentages  of  volume:  carbon  =  42.86, 
oxygen  =  57.14  =  100.00.  Its  specific  gravity  is  0.9678, 
air  =  i.oooo.  It  is  a  colorless,  tasteless,  combustible 
gas.  Pure  carbonic  oxide  forms  a  colorless,  transparent 
liquid  under  200  to  300  atmospheres  pressure  at  --  139° 
C.,  and  solidifies  to  a  snowy  mass  in  vacuo  at  —  21  r°  C. 

Carbonic  oxide  burns  with  a  blue  flame,  which  by  pre- 
vious heating  becomes  red,  generating  carbonic-acid  gas, 
COa.  The  temperature  of  its  flame  in  air  is  about  1400°  C. 
When  dry  it  is  not  changed  by  the  electric  current  nor  by 
ignited  platinum  wire,  but  when  standing  over  water  it  is 
decomposed  by  a  glowing  platinum  spiral ;  when  not  abso- 
lutely dry  it  may  be  exploded  with  oxygen  by  the  electric 
spark  or  by  platinum  wire  heated  to  300°  C.,  or  by  spongy 
platinum  at  ordinary  temperatures.  Two  molecules  of 
carbonic  oxide,  CO,  unite  with  I  atom  of  oxygen,  O,  to 
form  2  molecules  of  carbonic-acid  gas,  CO2.  The  combina- 
tion takes  place  very  slowly  in  the  presence  of  small  quan- 
tities of  steam,  and  increases  in  rapidity  with  the  quantity 
of  steam  present.  Hence  the  steam  acts  as  the  carrier  of 
oxygen  to  the  carbonic  oxide.  Small  quantities  of  other 
gases  than  steam  have  been  tried.  If  the  gas  contained 
no  hydrogen,  no  explosion  occurred.  When  a  mixture  of 
carbonic  oxide  and  steam  is  heated  to  about  600°  C.  a 
portion  of  carbonic  oxide  is  oxidized.  If  the  carbonic- 
acid  gas  is  removed  as  it  is  formed,  the  whole  may  be  oxi- 
dized. 

Carbonic  oxide  is  a  highly  poisonous  gas,  producing 
giddiness  and  ultimate  asphyxia  when  inhaled. 


106  COMBUSTION   OF   COAL. 

Q.  What  is  the  product  of  the  combustion  of   sulphur? 

Sulphur  combines  with  oxygen  to  form  sulphurous  oxide, 
SO2,  a  colorless  gas,  with  a  suffocating  odor.  It  is  a  non- 
supporter  of  combustion,  instantly  extinguishing  flame 
when  brought  within  its  influence.  Sulphurous  oxide,  in 
absorbing  vapor  of  water,  changes  from  sulphurous  oxide, 
SO2,  to  sulphurous  acid,  SO2,  H2O. 

Q.  What  is  the  effect  of  sulphur  in  coal  upon  the  sur- 
faces of  steam  boilers? 

If  the  sulphurous  oxide  generated  by  the  combustion  of 
sulphur  in  the  furnace  simply  passed  off  with  the  other 
products  of  combustion,  without  lodging  against  the  sur- 
faces of  the  boiler,  no  bad  effects  would  follow ;  but  nu- 
merous instances  are  on  record  where  sulphurous  oxide 
was  included  in  the  deposits  of  soot  in  contact  with  por- 
tions of  a  steam  boiler,  which  oxide  had  been  converted 
into  acid  by  the  subsequent  absorption  of  moisture.  The 
transformation  of  sulphurous  into  sulphuric  acid,  under 
the  action  of  water,  or  steam  and  air,  in  presence  of  a 
metal,  is  well  known,  and  exterior  corrosion  of  boilers  at- 
tributed to  the  action  of  smoke  is  wholly  confined  to  those 
parts  of  the  iron  which  were  wetted  by  infiltration  or  by 
accident. 

Q.  What  quantity  of  nitrogen  is  present  in  the  products 
of  combustion  ? 

Whatever  the  quantity  of  air  required  for  the  perfect 
combustion  of  carbon  or  hydrogen  there  will  remain  in  the 
furnace  3.35  pounds  of  nitrogen  for  every  pound  of  oxygen 
combined  with  the  fuel ;  or  by  volume  3.76  volumes  re- 
main in  the  furnace  for  each  volume  of  oxygen  uniting 
with  the  fuel. 


SURPLUS   AIR   IN    FURNACE.  IO/ 

Nitrogen  is  non-combustible,  and  so  far  as  the  other 
products  of  combustion  in  the  furnace  are  concerned  it  is 
wholly  inert. 

Q.  What  is  the  effect  of  surplus  air  in  the  furnace  in 
combination  with  the  products  of  combustion  ? 

Surplus  air,  or  air  in  excess  of  that  necessary  to  supply 
oxygen  to  the  burning  fuel,  acts  as  a  dilutant  of  the  fur- 
nace gases.  Inasmuch  as  this  surplus  air  has  to  be  heated 
by  the  furnace  to  the  temperature  of  the  escaping  gases,  it 
occasions  loss  by  abstracting  heat  from  the  furnace  gases, 
which  might  otherwise  be  employed  in  doing  useful  work. 

Q.  What  weight  of  gases  commonly  emerges  from  a 
steam-boiler  furnace  for  the  combustion  of  each  pound  of 
carbon  ? 

It  is  not  easy  to  carry  on  complete  combustion  by  means 
of  natural  draft  with  less  than  100  per  cent  excess  air; 
and  some  experiments,  made  by  Hoadley,  to  ascertain  the 
composition,  volume,  and  temperature  of  the  gases  from 
seventeen  boilers,  burning  good  anthracite  coal  at  known 
rate,  with  great  care,  and  under  most  favorable  conditions 
of  draft,  grate  area,  rate  of  combustion,  area  of  heating 
surface,  and  general  management,  gave  by  analysis  car- 
bonic-acid gas,  CO2  (no  carbonic  oxide,  CO),  nitrogen,  and 
free  atmospheric  air,  the  latter  being  one-half  the  whole. 

A  check  upon  the  accuracy  of  these  results  was  found 
in  the  temperature  of  the  furnace.  This  should  be,  with 
double  supply  of  air,  about  2600°  F.  It  was  found  to  be 
a  little  over  2400°  F.  It  appears  therefore  that  it  is  un- 
derstating rather  than  overstating  the  matter  to  say  that 
the  average  good  practice  would  show  a  double  supply  of 
air. 


108  COMBUSTION   OF   COAL. 

Q.  What  weight  of  gases  emerges  from  the  furnace  for 
perfect  combustion  of  one  pound  of  carbon  ;  also  the  ad- 
ditional weight  occasioned  by  air  in  excess  of  that  needed 
for  combustion? 

In  anthracite  coal  we  may  neglect  all  the  constituents 
except  carbon,  which,  when  perfectly  burned,  with  just 
sufficient  air  to  supply  the  oxygen,  will  produce  12.6 
pounds  of  mixed  gases  for  each  pound  of  carbon.  Thus  : 

Carbon i .  o         Carbon i .  oo 

Air ii. 6         Oxygen 2.66 


12.6  Product  CO2 3.60 

Nitrogen 8.94 


12.60 

Ib.  carbon  burnt  with      o%  excess  of  air  =12.6  Ibs.  gases. 
4.         ,«  50         «         ..     _  lg  ^    ,. 

"         loo         "         "     =  24.2    "        " 
125         ••         "     =  27.1     " 


Q.  What  is  included  in  the  term  ashes  ? 

The  term  ashes  includes  all  the  mineral  matter  left  on 
the  grates  after  the  complete  combustion  of  fuel.  Every 
variety  of  mineral  fuel  contains  more  or  less  incombustible 
matter  called  ashes.  The  presence  of  this  incombustible 
substance  in  coal  is  due  in  part  to  the  inorganic  matter 
contained  in  the  plants  of  which  the  coal  is  formed,  and 
partly  by  the  earthy  matter  in  the  drift  of  the  coal  period. 
The  inorganic  matter  thus  obtained  frequently  differs  both 
in  amount  and  in  proximate  composition  from  that  origi- 
nally present  in  the  unburnt  substance.  At  the  high  tem- 
perature of  burning  some  of  the  mineral  constituents  may 
be  volatilized,  or  be  mechanically  carried  away  by  the 


COMPOSITION    OF   ASHES.  IOQ 

gases  which  may  be  evolved,  and  changes  in  the  proximate 
nature  may  be  induced  either  by  the  heat  itself  or  by  the 
action  of  the  heated  carbonaceous  substances. 

Q.  What  is  the  specific  heat  of  ashes  ? 

The  specific  heat  of  ashes  may  be  assumed  to  be  0.215 
without  sensible  error  in  engineering  calculations. 

Q.  Of  what  do  ashes  principally  consist? 

Coal  ashes  are  found  to  consist  mainly  of  silica,  alumina, 
lime,  and  oxide  and  bisulphide  of  iron.  As  wood  contains 
from  i  to  3.5  per  cent  of  ash,  it  is  probable  that  much  of 
the  inorganic  matter  required  to  make  up  the  five  to  ten 
per  cent  in  coal  is  principally  earthy  substances  drifting 
into  and  incorporated  in  the  coal  during  its  formation. 
The  nature  and  color  of  coal  ashes  are  greatly  modified  by 
the  proportions  in  which  the  above  substances  are  united 
in  the  composition.  In  all  analyses  of  coal  ashes,  silica 
and  alumina  predominate. 

Q.  What  substances  are  found  in  analysis  of  ashes  of 
anthracite  coal? 

The  analysis  of  ashes  of  Pennsylvania  anthracite  coal, 
by  Professor  Johnson,  yielded : 

.    Silica 53. 60 

Alumina 36. 69 

Sesquioxide  of  iron 5. 59 

Lime 2. 86 

Magnesia i.oS 

Oxide  of  magnesia .19 


110  COMBUSTION   OF   COAL. 

Q.  What  substances  are  found  in  the  analysis  of  ashes 
from  bituminous  coal  ? 

Ohio  bituminous  coal,  containing  5.15  per  cent  of  ash, 
yielded  upon  analysis : 

Silica 58.  75 

Alumina  35. 30 

Sesquioxide  of  iron 2.09 

Lime i .  20 

Magnesia o.  68 

Potash  and  soda 1.08 

Phosphoric  acid o.  13 

Sulphuric  acid o.  24 

Sulphur  combined 0.41 


99.88 

Block  coal  is  a  non-caking,  bituminous  coal  found  in 
Indiana.  It  occurs  in  thin  laminae,  separated  by  fibrous 
charcoal  partings,  with  fractures  occurring  in  the  coal  at 
right  angles  to  the  bed.  A  sample  of  this  coal  yielded 
2.  5  per  cent  of  white  ash,  of  which  the  composition  was : 

Alumina 48.00 

Sesquioxide  of  iron 32. 80 

Silica,  lime,  magnesia,  etc 19. 20 


100.00 

Of  the  sulphur  present  in  this  coal, 

.947  per  cent,  was  in  combination  with  iron. 
.483       "  with  other  constituents. 


1.430       "  of  sulphur  in  the  sample. 

Q.  What  does  the  color  of  coal  ashes  indicate? 

Coal  ashes  are  usually  either  white,  brown,  or  variously 
tinged  with  red.  It  is  a  common  designation  'to  say  of 
coals  that  they  are  white-ash  or  red -ash.  When  the 
amount  of  iron  is  very  small,  or  not  sufficient  to  tinge  the 


COLOR    OF    ASHES.  Ill 

ashes,  they  are  then  usually  white.  A  larger  quantity  of 
iron  produces  a  red-ash.  Thus  the  color  enables  one  to 
judge  of  the  probable  nature  of  the  ashes,  whether  they 
will  clinker  in  the  fire  or  not.  The  intensity  of  the  red 
color,  taken  in  connection  with  the  amount  of  ashes  in 
coal,  may  also  serve  as  an  indication  of  the  proportion  of 
sulphur  existing  in  the  state  of  pyrites. 

Q.  Judging  from  the  color  of  the  ash  alone,  which 
coals  will  clinker  least  under  high  temperatures  ? 

Those  coals  are  best,  the  ashes  of  which  are  of  nearly 
pure  white,  and  which  with  large  amounts  of  silica  and 
alumina  in  their  composition,  contain  little  or  no  alkali, 
nor  any  lime,  nor  oxide  of  iron.  Of  this  character  are  the 
earthy  residue  of  the  best  white-ash  anthracites  of  Penn- 
sylvania, and  in  an  eminent  degree  the  ashes  of  some  of 
the  semi-anthracites.  In  general,  it  requires  a  high  tem- 
perature to  fuse  these  ingredients  when  taken  by  them- 
selves, but  the  presence  of  the  oxide  of  iron  tends  to  lower 
the  point  of  fusion. 

Q.  Will  not  all  coal  ashes  fuse,  or  clinker,  under  in- 
tense heat  ? 

There  are,  perhaps,  no  coals  whose  ashes,  when  exposed 
to  the  extremest  heats  procurable  by  artificial  blasts,  will 
not  soften  to  a  cohering  cinder,  or  even  melt  in  part  into 
a  stony  clinker ;  but  as  the  tendencies  to  these  several  de- 
grees of  fusion  are  very  various,  it  proves  to  be  a  distinc- 
tion affecting  the  practical  value  of  coals,  which  is  of  the 
utmost  importance.  In  domestic  consumption,  where  the 
heat  of  combustion  is  comparatively  moderate,  the  quan- 
tity rather  than  the  quality  or  fusibility  of  the  ashes  is  the 
point  of  greatest  consideration;  but  where  an  excessive 


112  COMBUSTION   OF  COAL. 

and  melting  heat  is  required,  as  in  many  modes  of  gener- 
ating steam,  the  practicability  of  employing  a  coal  at  all 
will  oftentimes  be  determined  by  this  one  quality  of 
clinkering  of  the  ashes. 

Q.  What  is  the  effect  of  the  presence  of  oxide  of  iron 
in  coal  ashes  ? 

The  amount  of  the  oxide  of  iron  present  in  coal  ashes 
is  one  of  great  importance,  especially  as  it  unites  with  pot- 
ash, soda,  lime,  and  silica,  also  present,  to  form  clinker. 
The  presence  of  oxide  of  iron  in  ashes,  when  in  any  con- 
siderable quantity,  may  be  detected  without  analysis  by 
the  red  color  imparted  to  them.  The  particular  objection 
to  the  combination  and  fusing  of  the  silica,  lime,  potash, 
etc.,  in  the  ashes  of  the  coal  into  a  vitreous  mass  is  that, 
unless  the  greatest  care  is  exercised,  it  will  accumulate 
upon  the  grate  bars  in  sufficient  quantity  to  exclude  the 
passage  of  the  air  needed  for  combustion,  and  thus  lower 
the  temperature  of  the  furnace. 

Q.  How  is  the  presence  of  the  oxide  of  iron  accounted 
for  in  coal  ashes  ? 

Nearly  every  variety  of  coal  contains  more  or  less  iron 
pyrites.  This  is  the  probable  source  of  the  oxide  of  iron 
in  ashes.  The  greater  part  of  the  sulphur  being  expelled 
by  heat,  its  equivalent  of  oxygen  unites  with  the  iron, 
with  which  hydrogen  also  combines,  forming  the  sesqui- 
oxide  of  iron  occurring  in  the  analysis  of  coal  ashes. 

Q.  What  is  the  effect  of  iron  pyrites  included  in  the 
ashes  of  coal? 

Coal  always  contains  more  or  less  of  sulphur  in  its  com- 
position, and  this  sulphur  occurs  mainly  as  a  native  bisul- 


SULPHUR   IN   ASHES. 


phide  of  iron,  or  iron  pyrites,  a  mineral  of  bright  yellow 
color  often  mistaken  for  gold.  Pyrites  approximate  equal 
parts  of  iron  and  sulphur  with  a  ten-per-cent  variation  on 
either  side.  About  one-half  the  sulphur  may  be  driven 
off  by  heat ;  and  if  the  fire  is  intense,  the  remaining  por- 
tion of  the  pyrite  is  present  in  the  ashes  as  a  black  sul- 
phuret  of  iron,  which,  in  combination  with  other  sub- 
stances, may  form  a  hard  clinker,  difficult  to  remove  from 
the  grates  if  once  allowed  to  cool. 

Unless  the  conditions  are  favorable  a  less  percentage 
of  sulphur  is  distilled  from  the  pyrites  than  that  noted  in 
the  preceding  paragraph,  as  indicated  in  tests  made  in 
Germany,  on  coals  of  the  carboniferous  period : 

TABLE  n.—  SULPHUR  EVOLVED  IN  THE  BURNING  OF  COAL  AND 
RETAINED  IN  THE  ASHES. 


Ash  in  100 
pounds  of  coal. 

Sulphur  in  100 
pounds  of  coal. 

Sulphur  in  100 
pounds  of  ash. 

Sulphur  in  the 
ash  from  100 
pounds  of  coal. 

Sulphur  evolved 
in  burning  100 
pounds  of  coal. 

Pounds. 
7.360 
5.760 
16.530 

Pounds. 
0.789 

O.Q73 
3.264 

Pounds. 
9.464 
14-663 
18.174 

Pounds. 
0.696 
0.844 
2.424 

Pounds. 
0.093 
0.129 
0.840 

Q.  Is  sulphur  always  present  in  coal  as  iron  pyrites  ? 

There  is  no  doubt  that  sulphur  is  present  in  coal  in 
combination  with  the  organic  elements  of  which  it  is  com- 
posed ;  but  what  the  definite  compound  may  be  which  con- 
tains it  is  unknown.  For  example,  a  coal  from  New 
Zealand  containing  2.  50  per  cent  of  sulphur  yielded  an 
ash  remarkably  white;  the  coke  contained  2. 35  per  cent  of 
sulphur.  No  sulphuric  acid  was  detected  in  the  hydro- 
chloric acid  in  which  the  powder  of  the  coal  had  been 

boiled.      It  would  appear  that  the  sulphur  was  present  in 
s 


114  COMBUSTION   OF   COAL. 

the  same  state  of  combination  in  the  coal  as  that  in  which 
it  exists  in  albumin,  fibrine,  etc. ;  for  it  could  not  have 
been  combined  with  iron,  as  in  this  case  the  ash  would 
have  had  a  decided  red  color. 

Q.  What  is  clinker  ? 

Clinker  is  a  product  formed  in  the  furnace  by  fusing 
together  the  impurities  in  the  coal,  such  as  oxide  of  iron, 
silica,  lime,  etc.  There  are  few  colored  ashes,  and  espec- 
ially red  ashes,  that  will  not  soften  under  the  action  of  in- 
tense heat  and  form  clinker;  white-ash  coals  produce  the 
least  clinker. 

Q.  How  is  alumina  present  in  ashes  ? 

Alumina  is  the  oxide  of  the  metal  aluminum ;  it  is  the 
pure  earth  of  clay.  It  is  infusible  in  any  temperature  yet 
obtained  in  furnaces.  The  alumina  present  in  ashes  is  in 
the  form  of  a  clay  or  a  mixture  of  the  two  simple  earths, 
alumina  and  silica,  generally  tinged  with  iron.  The  floor, 
or  pavement,  immediately  under  the  coal  beds  is,  almost 
without  exception,  a  grayish  slate-clay,  which  strongly  re- 
sists the  fire.  This  clay  varies  in  thickness  from  a  frac- 
tion of  an  inch  to  many  feet,  and  is  often  disseminated 
through  the  shale  found  in  coal. 

The  presence  of  alumina  in  analyses  of  wood  ashes  from 
trees,  such  as  beech,  pine,  fir,  etc.,  is  not  easily  accounted 
for  inasmuch  as  no  inorganic  substance  can  find  its  way 
into  a  plant  except  in  a  state  of  solution  in  water,  when  it 
is  absorbed  by  the  roots ;  and,  certainly,  neither  rain  water 
nor  ordinary  mineral  water  contains  any  salt*  of  alumina, 
nor  does  water  impregnated  with  carbonic  acid,  which  dis- 
solves phosphate  of  lime  or  magnesia,  dissolve  even  a  trace 
of  phosphate  of  alumina. 


SILICA    IN   ASHES.  11$ 

Ashes  of  lycopodium  contain  from  52  to  57  per  cent  of 
alumina,  13  per  cent  of  silica,  and  12  per  cent  of  potash. 
This  species  of  plants  has  contributed  largely  to  the  pro- 
duction of  coal.  It  appears,  therefore,  that  the  inorganic 
matter  in  coal,  of  which  alumina  is  a  notable  constituent, 
may  have  been  in  great  measure  derived  from  that  origin- 
ally existing  in  the  coal-forming  plants,  and  the  alumina 
originally  present  in  these  plants  would  be  uniformly  dif- 
fused through  the  mass  of  coal. 

Q.  How  is  silica  present  in  ashes  ? 

The  only  known  oxide  of  silicon  [symbol,  Si. ;  atomic 
weight  =  28.33]  occurs  abundantly  in  nature,  pure,  or 
nearly  so,  in  quartz,  flint,  etc.  It  enters  largely  into  the 
constitution  of  sandstones,  felspar,  and  many  other  rocks. 
Silica,  known  also  as  silicic  acid,  silex  (formula,  SiO2),  is 
infusible  except  at  very  high  temperatures;  it  is  non-vola- 
tile; it  decomposes  fused  sodium  carbonate  and  melts  to  a 
transparent  glass.  It  is  insoluble  in  water  and  all  acids 
except  hydrofluoric  acid,  which  decomposes  it  into  water 
and  silicon  fluoride.  Silica  dissolves  readily,  as  a  rule,  in 
caustic  alkalies,  forming  solutions  of  alkaline  silicate 
(water-glass).  Silica  is  decomposed  at  a  red  heat  by  car- 
bon in  presence  of  iron  and  at  white  heat  by  carbon  mon- 
oxide, CO,  a  metallic  silicide  being  formed. 

Silica  plays  a  very  important  part  in  the  formation  of 
slags,  and  fusion  is  not  necessarily  required  to  produce 
combination.  Thus,  when  certain  mixtures  of  silica  and 
lime  are  strongly  heated,  there  is  not  the  slightest  indica- 
tion of  fusion,  yet  it  is  certain  that  the  silica  has  entered 
into  combination.  The  bases  which  most  frequently  occur 
in  slags  are  lime,  magnesia,  protoxide  of  iron,  potash  in 
small  quantity,  and  alumina. 


u6 


COMBUSTION   OF   COAL. 


Silica  is  an  abundant  element  in  the  ashes  of  straw,  as 
shown  in  the  following : 

Per  Cent. 

Potassa 10.  51 

Soda 1.03 

Lime 5.91 

Magnesia 1.25 

Sesquioxide  of  iron 0.07 

Sulphuric  acid 2.14 

Silica 73.  57 

Phosphoric  acid 5.51 


Total 99. 99 

Q.  How  is  potash  present  in  ashes  ? 

Potash  occurring  in  ashes  is  in  various  states  of  combi- 
nation, as  carbonate,  sulphate,  and  as  chloride  of  potash. 
The  percentage  of  potash  is  much  greater  in  wood  than  in 
coal  ashes.  The  following  table  (12)  shows,  according  to 
Hoss,  the  proportions  of  ash  and  potash  in  some  of  the 
leading  woods : 


TABLE  12. — POTASH  CONTAINED  IN  ASHES  OF  SEVERAL  WOODS. 


Wood. 

Ash 
Per  Cent. 

Potash 
Per  Cent. 

Pine  

.34 

.Ojc 

Beech 

c8 

127 

Ash 

I   22 

071 

Oak 

I   3^ 

ICQ 

Elm             .... 

2.  tic 

-3QO 

Willow     .        .                

2  80 

281 

Pure,  dry  carbonate  of  potash  is  a  hard,  white  solid, 
specific  gravity  of  2.207,  having  a  strong  alkaline  reaction 
and  taste.  It  melts  at  a  full  red  heat,  and  at  a  higher 
temperature  slowly  volatilizes. 


LIME    PRESENT    IN   ASHES.  117 

The  following,  from  Berthier's  original  analysis,  shows 
the  composition  of  pine-tree  ash : 

Solution  in  water:  Per  Cent. 

Carbonate  of  potash i.  86 

Sulphate  of  potash 3. 63 

Chloride  of  potash 1.88 

Carbonate  of  soda 6. 03 

Silica 18 

Insoluble  in  water : 

Lime 38.51 

Magnesia 9.  56 

Oxide  of  iron 09 

Oxide  of  manganese 36 

Carbonic  acid 32. 77 

Phosphoric  acid 91 

Silicic  acid 4. 19 

99-97 

Q.  How  is  lime  present  in  ashes? 

Lime  occurring  in  ashes  is  a  product  of  one  of  the  car- 
bonates present  in  the  coal,  in  which  its  contained  carbonic 
acid  is  driven  off  by  heat,  leaving  a  white  or  pale  gray 
substance,  acrid  and  caustic  to  the  taste,  and  exhibits  a 
powerful  alkaline  reaction.  Lime  heated  by  itself  is  one 
of  the  most  refractory  substances  known,  and  no  temper- 
ature has  as  yet  been  attained  which  has  caused  it  to  ex- 
hibit the  slightest  indication  of  fusion  ;  but  lime  promotes 
the  fusiqn  of  some  other  oxides  in  a  remarkable  manner, 
and  hence  it  is  used  as  a  flux.  Carbonate  of  lime  is  an 
essential  ingredient  in  all  fertile  soils,  and  occurs  in  every 
kind  of  rock. 

Q.  How  do  the  substances  which  form  clinker  affect  the 
efficiencies  of  coals? 

The  several  substances,  silica,  lime,  potash,  etc.,  occur- 
ring in  coal  ashes  are  variable  in  their  nature ;  and  thus 


Il8  COMBUSTION   OF   COAL. 

by  the  forms  they  take  under  different  intensities  of  com- 
bustion much  affect  the  efficiencies  of  the  coals  to  which 
they  belong.  Being  differently  fusible  themselves,  and 
affecting  differently  the  fusion  of  each  other,  no  two  of  the 
earths,  alkalies,  or  metallic  oxides  of  the  ashes  but  differ 
in  their  agency  when  subjected  to  an  elevated  heat;  and 
their  mutual  reactions  are  moreover  changed,  as  the  tem- 
peratures are  changed  to  which  they  are  exposed.  It 
hence  arises  that  the  residue  from  many  coals  melts  to  a 
large  extent,  under  no  very  intense  combustion,  into  vari- 
ous descriptions  of  hard,  semi-vitreous  slags;  others  yield 
a  less  stony  clinker ;  and  some  again  at  a  far  more  elevated 
heat  result  only  in  a  partially  agglutinated,  spongy,  open 
cinder,  or  even  in  a  pulverulent  or  flaky  ash. 

Q.  What  quantity  of  ash  is  present  after  the  complete 
combustion  of  coal  ? 

The  percentage  of  ash  varies  considerably  for  different 
coals,  but  it  is  generally  less  in  anthracite  than  in  the  bi- 
tuminous varieties.  Taking  hard  and  soft  coals  as  a  whole, 
the  average  quantity  of  ash  will  lie  between  five  and  ten 
per  cent,  with  occasional  variations  on  either  side. 

Q.  What  is  smoke? 

Smoke  is  a  general  term  often  applied  to  all  the  prod- 
ucts of  combustion  escaping  from  the  furnace,  whether 
visible  or  invisible.  In  a  more  restricted  application  it 
denotes  the  sooty  products  of  the  furnace  escaping  with 
the  waste  gases.  These  sooty  particles  are  solid  carbon, 
and  usually  very  light  and  small.  So  far  as  mere  weight 
is  concerned,  the  blackest  smoke  is  not  perceptibly  heavier 
than  if  the  products  of  combustion  were  transparent.  The 
objection  to  black  smoke,  as  such,  is  not  the  actual  loss  in 


SMOKE    PREVENTION.  IIQ 

weight  of  carbon.  It  is  rather  that  in  cities  and  towns 
these  sooty  particles  find  their  way  through  the  ordinary 
currents  of  air  into  business  places,  dwellings,  etc.,  the 
sooty  deposit  being  practically  constant  in  the  neighbor- 
hood of  such  a  chimney,  causing  much  annoyance  to 
housekeepers,  merchants,  and  others.  Colored  smoke  is  a 
product  of  incomplete  combustion. 

Q.  Is  colored  smoke  then  no  indication  of  waste  in 
furnace  combustion  ? 

Colored  smoke  is  sure  evidence  of  wasteful  combustion, 
because  it  indicates  a  low  temperature  of  furnace.  An- 
thracite coal  and  coke  give  off  no  sooty  particles  when 
burning.  In  the  case  of  bituminous  coal  the  first  effect 
of  the  heat  is  to  detach  small  particles  of  carbon  from  the 
surfaces  next  the  incandescent  fuel  on  the  grate.  These 
particles  are  so  light  that  they  are  easily  carried  out  of  the 
furnace  and  up  the  chimney  by  the  mechanical  agency 
of  the  draft.  If  the  furnace  temperature  was  sufficiently 
high,  and  there  was  enough  free  oxygen  over  the  bed  of 
fuel  to  burn  these  soot  particles,  they  would  be  converted 
into  carbonic-acid  gas  and  become  wholly  invisible. 
Black  smoke  is  not  a  product  of  a  high,  but  always  that  of 
a  low  furnace  temperature. 

Q.  How  may  smoke  prevention  be  accomplished  ? 

Bituminous  coals,  rich  in  hydrocarbons,  require  a  fur- 
nace of  much  greater  cubic  content  to  render  their  com- 
bustion complete  and  wholly  smokeless,  than  is  required 
for  anthracite  coal  or  coke.  The  combustion  chamber  for 
bituminous  coal  ought  always  to  be  large  and  roomy.  The 
temperature  must  always  be  high.  Provision  must  be 
made  for  a  controlled  air  admission  above  the  fuel  to  sup- 


120  COMBUSTION   OF   COAL. 

ply  the  additional  oxygen  required  for  the  conversion  of 
the  carbonic  oxide  into  carbonic-acid  gas.  The  fuel  should 
be  free  from  large  lumps,  and  either  frequently  or  con- 
tinuously fed  to  the  furnace. 

In  admitting  air  above  the  fuel,  unless  it  can  be  sup- 
plied at  the  right  place  and  time,  and  in  the  right  quan- 
tity, it  may  prove  a  worse  evil  than  the  smoke  itself,  by 
lowering  the  temperature  of  the  gases  in  the  furnace  to 
a  point  below  which  ignition  is  insured. 

In  an  ordinary  boiler  furnace,  with  flat  grates,  a  nearly 
smokeless  fire  can  be  maintained  by  breaking  up  the  coal 
and  banking  it  immediately  inside  the  fire  door,  that  the 
gases  may  distill  from  the  coal  slowly.  These  gases  pass- 
ing over  the  bed  of  incandescent  coke,  through  which  an 
excess  of  air  is  passing,  will  burn  the  volatile  combustible 
of  the  coal  smokelessly.  When  the  fuel  is  well  coked,  it 
can  be  broken  up,  distributed  over  the  grates,  and  a  fresh 
supply  of  raw  coal  banked  up  as  before. 

Q.  What  rule  is  there  for  measuring  the  shades  of  in- 
tensity of  smoke? 

In  any  thorough  study  of  smoke  a  scale  of  intensity  is 
very  important.  As  to  the  number  of  shades  of  intensity 
it  has  been  proposed  variously  from  three  to  ten.  The  lat- 
ter was  adopted  by  the  South  Kensington  and  Manchester 
Smoke  Abatement  Commissions  (1881),  and  upon  trial 
was  found  to  be  quite  undesirable,  as  it  was  difficult  to 
discriminate  between  so  many  slightly  differing  shades. 
The  second  English  Smoke  Commission,  in  1895,  adopted 
a  scale  of  only  three  shades — faint,  medium,  and  black; 
but  three  shades  were  found  to  be  too  few,  as  ten  were 
found  to  be  too  many. 

The  best  scale  to  adopt,  according  to  the  view  now  held 


RINGLEMANN'S    SMOKE    SCALE.  121 

by  most  of  the  authorities,  seems  to  be  one  having  five 
shades,  viz. : 

1.  White  transparent  vapor. 

2.  Light  brown  smoke. 

3.  Brownish-gray  smoke. 

4.  Dense  smoke. 

5.  Thick  black  smoke. 

The  determining  of  the  different  shades  is  largely  em- 
pirical, the  shade  varying  with  each  observer  according  to 
his  sight  and  sense  of  color. 

Professor  Ringlemann's  smoke  scale  adopts  the  five 
shades,  and  his  plan  is  to  represent  the  different  grays 
into  which  the  shades  of  smoke  are  naturally  divided  by 
black  cross  lines  on  white  paper.  Seen  at  a  given  dis- 
tance from  the  observer,  these  black  and  white  diagrams 
show  different  shades  of  gray,  representing  the  desired 
smoke  tints.  Variations  in  the  shade  can  be  obtained  by 
varying  the  thickness  of  black  lines  or  the  size  of  the  in- 
terstices of  white  left  between  them.  A  given  cross  line 
arrangement  will  represent  one  shade  of  gray  when  seen 
at  a  distance,  say,  of  80  to  100  feet  from  the  observer, 
while  if  the  black  lines  be  doubled  in  thickness  and  the 
white  intervals  between  them  correspondingly  diminished 
by  half,  another  and  darker  shade  of  gray  will  at  the  same 
distance  be  shown  (see  Fig.  3). 

The  principles  on  which  the  Ringlemann  smoke  scales 
are  designed  are  as  follows  : 

No.  o.     No  smoke.     All  white. 

1.  Light  gray  smoke.      Black  lines   i   mm.   thick,  and 
white  spaces  of  9  mm.  between,  all  crossed  at  right  angles 
like  a  chess  board. 

2.  Darker  gray  smoke.     Black  lines  2.3  mm.  thick,  7.7 
mm.  apart. 


No.  1. 


No.  2. 


No.  3,  No.  4. 

FIG.  3 — Professor  Ring-lemann's  Smoke  Chart. 


SMOKELESS    FIRING    IN    LOCOMOTIVES.  123 

3.  Very  dark  gray  smoke.      Black  lines  3.7  mm.  thick, 
6.  3  mm.  apart. 

4.  Black  smoke.      Black  lines  5.5   mm.  thick,  4.5  mm. 
apart. 

5.  Very  black  smoke.     All  black. 

This  is  probably  the  best  smoke  scale  yet  produced.  It 
is  in  use  in  portions  of  England,  France,  and  in  the  United 
States. 

Q.  Can  soft  coal  be  burned  without  smoke  in  ordinary 
locomotive  fire  boxes? 

That  railway  smoke  nuisance  can  be  almost,  if  not 
wholly,  abated,  by  simply  exercising  proper  care  and  judg- 
ment in  firing,  is  the  expressed  opinion  of  Mr.  Angus 
Sinclair,  an  engineer  of  wide  experience  and  excellent 
judgment.  His  recommendations,  based  upon  actual  prac- 
tice, consist  merely  in  reducing  the  coal  to  small  sizes,  no 
large  lumps,  and  firing  in  what  is  known  as  the  single- 
shovelful  method. 

The  practical  working  of  this  method  of  firing  has 
shown,  according  to  the  records  of  the  Burlington,  Cedar 
Rapids  &  Northern  Railway,  that  bituminous  coal  burning 
locomotives,  without  any  specially  contrived  fire  box  or  fix- 
tures (except  the  ordinary  brick  arch),  can  be  operated  in 
any  service  from  yard  switching  to  heavy  freight  trains, 
quite  as  smokeless  as  if  anthracite  coal  were  used.  This 
method  of  firing  now  permits  passenger  trains  to  be  run 
comfortably  over  that  road  with  the  windows  open.  Fur- 
ther, an  economy  of  about  one-sixth  of  the  money  former- 
ly paid  for  coal  is  now  saved  to  the  company ;  the  engines 
steam  much  more  freely  than  under  the  old  method  of 
heavy  intermittent  firing;  the  annoyance  of  leaky  tubes 
has  almost  ceased ;  there  is  no  filling  up  of  smoke  boxes 


124 


COMBUSTION    OF    COAL. 


with  cinders ;  and  there  has  been  a  decided  reduction  in 
the  work  of  the  boiler-maker;  and  last,  but  not  least,  the 
fireman  has  less  work  of  coal-throwing  to  do,  and  he  and 
the  engineer  are  acting  together  to  produce  satisfactory 
results. 

Q.  What  results  have  been  accomplished  on  the  Cin- 
cinnati, New  Orleans  &  Texas  Pacific  Railway  in  smoke- 
less firing  with  bituminous  coal? 

Mr.  J.  W.  Murphy,  superintendent  of  the  above  road, 
says  there  is  no  detail  in  connection  with  the  operation  of 


I  *   '  «l- 

-  7 

tl'p 

"-»'— 

I  -S"TUBE 

i 

'- 

FIG.  4. 

the  road  to  which  the  management  gives  so  much  special 
and  continued  attention  as  in  the  efforts  to  prevent  the 
emission  of  black  smoke  by  locomotives  on  passenger 
trains. 

To  secure  these  results,  it  was  necessary,  first,  to  equip 
the  engines  with  brick  arches,  as  indicated  in  Fig.  4. 
Four  holes  are  shown  on  each  side  of  the  fire  box  for  the 
purpose  of  admitting  air.  Four  tubes  run  through  the 
arch,  and  the  outside  air,  passing  through  these  tubes,  is 


INSTRUCTIONS   TO    FIREMEN.  12$ 

heated  to  a  high  temperature.  This  heated  air  supplies 
oxygen  to  the  unconsumed  gases  and  produces  complete 
combustion.  The  four  holes  in  each  side  of  the  fire  box 
are  located  twelve  inches  above  the  grates,  and  into  these 
openings  are  inserted  the  Sharp  patent  deflecting  air  tubes, 
deflecting  the  air  to  the  fire. 

Q.  What  instructions  were  issued  to  engineers  for  firing 
passenger  locomotives  on  the  "  Queen  and  Crescent  Limited, " 
Cin.,  N.  0.  &  T.  P.  Ry.? 

After  firing  each  shovelful  of  coal,  the  door  must  be  left 
open  one  or  two  inches  for  a  few  seconds,  admitting  enough 
air  to  produce  complete  combustion  of  the  gases  driven  off 
from  the  coal.  Care  must  be  taken  not  to  leave  the  door 
open  longer  than  necessary  to  consume  the  gases. 

Firemen  must  learn  to  work  with  as  light  a  fire  as  pos- 
sible. Great  care  must  be  taken  that  steam  is  not  wasted 
at  the  safety  valve,  either  when  the  train  is  in  motion  or 
when  standing  still. 

Before  starting,  the  blower  must  be  put  on  and  a  suffic- 
ient supply  of  coal  put  into  the  fire  box  to  insure  a  good 
solid  fire.  After  the  coal  has  been  put  in,  the  door  must 
be  left  partly  open  by  placing  the  latch  on  the  first  notch 
of  the  catch,  so  to  remain  until  the  smoke  entirely  disap- 
pears, when  the  door  must  be  closed. 

After  starting  the  door  must  be  left  partly  open  after 
each  shovelful  of  coal  is  put  into  the  fire  box,  by  placing 
the  latch  on  the  first  notch  of  the  catch  until  such  time  as 
the  smoke  disappears,  when  the  door  must  be  closed. 

On  approaching  tunnels  the  fire  must  be  replenished  in 
ample  time,  obtaining  sufficient  fire  to  carry  the  train 
through  the  tunnel  without  smoke,  the  door  to  be  kept 
closed  while  passing  through  tunnels, 


126  COMBUSTION    OF   COAL. 

The  engineman  should  so  arrange  the  water  supply  that 
the  fireman  may  be  able  to  fire  the  engine  regularly  and 
economically,  and  this  can  be  done  best  when  the  water  is 
supplied  to  the  boiler  continuously. 

Firemen  must  pay  particular  attention  to  the  manner 
in  which  the  engineman  works  the  injector  and  handles 
the  engine,  in  order  to  regulate  the  fire  accordingly. 

*  Care  must  be  taken  to  have  the  blower  applied  and  the 
door  partly  open  when  approaching  a  station  where  a  stop 
is  to  be  made,  and  no  smoke  must  be  allowed  to  show 
from  the  stack  at  such  times  or  when  descending  grades. 

While  the  blower  is  being  used,  except  when  approach- 
ing a  station  where  a  stop  is  to  be  made,  care  should  be 
taken  to  keep  the  door  closed  as  much  as  possible,  more 
especially  when  cleaning  the  fire,  as  the  blower  causes  the 
cold  air  to  be  drawn  into  the  flues. 

While  lying  on  side  tracks,  both  dampers  should  be 
closed  to  save  the  fire. 

Grates  should  be  shaken  only  when  absolutely  neces- 
sary, as  too  frequent  shaking  causes  a  loss  of  fuel  by  al- 
lowing the  unconsumed  coal  to  fall  into  the  ashpan,  where 
it  ignites  and  causes  the  pan  to  heat  and  warp.  Ashpans 
should  be  examined  as  frequently  as  stops  will  permit,  and 
under  no  circumstances  must  they  be  allowed  to  become 
filled. 

When  possible  to  avoid  it,  the  fire  box  must  not  be  left 
wide  open.  To  leave  the  fire  door  wide  open  is  especially 
bad  when  using  steam  or  blower. 

It  is  beneficial  to  wet  the  coal  before  firing,  and  firemen 
should,  as  far  as  possible,  use  wet  coal. 

Intelligent  firing  and  economical  results  in  the  use  of 
fuel  will  be  considered  in  the  selection  of  firemen  for  pas- 
senger engines  or  for  promotion  to  freight  enginemen. 


SMOKELESS    COMBUSTION.  I2/ 

These  rules  must  be  strictly  observed  on  night  as  well 
as  on  day  passenger  trains. 

Q.  How  may  smokeless  combustion  be  best  secured  in 
locomotive  practice  ? 

The  best  examples  of  smokeless  firing  occur  in  locomo- 
tives using  no  device  but  the  brick  arch  in  connection 
with  careful  firing.  A  general  sentiment,  based  upon  ex- 
perience on  Western  railroads,  where  soft  coal  only  is  used 
for  fuel,  is  that  a  good  fireman  without  a  special  device  is 
productive  of  better  results  than  any  of  the  mechanical 
devices  if  poorly  managed.  The  conclusion  reached  in 
Chicago,  St.  Louis,  and  other  Western  cities  where  efforts 
have  been  made  to  reduce  the  amount  of  smoke  made  by 
locomotives,  is  that  steam  jets  and  other  similar  devices 
are  not  to  be  seriously  considered  as  successful  smoke 
preventives;  and,  second,  the  most  effectual  method  of 
preventing  smoke  is  by  the  use  of  the  brick  arch  and  skil- 
ful firing. 

Q.  What  is  the  device  for  smoke  prevention  by  the 
Locomotive  Smoke  Preventer  Company? 

This  device  as  applied  to  a  locomotive  is  shown  in  Fig. 
5,  and  further  illustrated  in  detail  in  Fig.  6,  which  shows 
the  heating  coil  in  the  smoke-box  extension;  Fig.  6a, 
which  is  another  view  of  the  heating  coil ;  Fig.  7,  which 
shows  plan  arrangement  of  the  manifold,  a  group  of  three 
jets  passing  through  the  front  end  of  the  fire  box;  Fig.  8, 
an  enlarged  section  of  the  combined  steam  and  air  jet, 
and  the  seamless  water  jacket.  The  elevation  of  a  loco- 
motive (Fig.  5)  shows  the  entire  device  when  applied;  it 
consists  of  a  funnel-shaped  pipe  A,  which  is  attached  to 
the  smoke  box  at  B ;  this  pipe  continues  to  one  end  of  a 


128 


COMBUSTION    OF    COAL. 


LOCOMOTIVE    SMOKE   PREVENTER   COMPANY. 


29 


series   of   bends  or  coils  of   pipe    called    the    heater   C, 
whose  axis  is  parallel  with  the  axis  of  the  boiler  shell — 


FIG.  6. 


the  other  end  being  attached  to  a  pipe  which  leaves  the 
smoke  box  at  D  on  the  opposite  side  from  A.  By  means 
of  an  elbow  it  connects  to  the  pipe  E  extending  along  the 
side  of  the  boiler  close  under  the  running  boards  back  to  a 


FIG.  7. 


point  in  front  of  the  throat  sheet — where  by  45°  elbows  it 
passes  under  the  barrel  and  enters  at  the  centre  of  the 
9 


130 


COMBUSTION    OF   COAL. 


manifold  F  placed  in  front  and  close  to  the  throat  sheet. 
The  three  or  more  openings  in  the  manifold  exactly  tally 
with  the  air  ducts  leading  into  the  fire  box.  In  the  inside 


of  the  fire  box  at  the  tube  sheet  and  close  to  the  under 
side  of  the  fire-brick  arch  are  three  or  more  cylindrical 
tapered  water-jackets,  G,  G,  which  screw  into  the  tube 
sheet  and  extend  into  the  fire  box  a  distance  of  about 
twelve  or  fourteen  inches,  their  interior  being  open  direct 
to  the  water  leg  of  the  boiler;  concentric  with  the  jacket 


FIG.  9. 


and  extending  from  the  throat  sheet  through  the  water  leg 
and  jacket  is  the  air  tube  H  referred  to  above,  its  ends 
being  expanded  and  beaded  into  the  sheet  and  jacket  re- 
spectively. It  will  thus  be  seen  that  we  have  a  contin- 


OBJECTION   TO    STEAM   AND    AIR   JETS.  131 

uous  air  passage  from  the  air  funnel  at  the  front  of  the 
engine  through  the  hot  smoke  box  to  the  fire  zone  in  the 
fire  box. 

A  side  elevation  and  plan  of  manifold  F,  together  with 
the  method  of  attaching  the  steam  jets,  is  shown  in  Figs. 
7  and  8.  The  manifold  is  tapped  for  a  one-fourth  inch 
pipe  terminating  in  an  one-eighth  inch  opening  in  the  air 
tube  H.  The  flow  of  steam  through  it  is  controlled  by  a 
valve  J  in  the  cab.  The  special  function  of  this  jet  is  to 
force  hot  air  into,  the  fire  box  when  the  engine  is  at  rest, 
or  when  running  with  the  throttle  shut.  When  an  appli- 
cation of  coal  is  made,  it  is  met  by  a  large  volume  of  air 
heated  to  the  point  of  ignition  by  previous  contact  with 
the  incandescent  fire-brick  arch,  thus  furnishing  oxygen 
where  it  is  most  needed  to  produce  smokeless  combustion. 

The  door  sheet  nozzles  shown  in  Fig.  9  are  used  on  en- 
gines having  long  fire  boxes  and  a  comparatively  short  fire- 
brick arch. 

Q.  What  is  the  objection  to  a  combined  steam  and  air 
jet  in  a  locomotive  furnace  ? 

Steam  jets  which  introduce  both  steam  and  air  above 
the  fire  have  a  temporary  dampening  effect  when  the  en- 
gine is  standing,  as  they  produce  a  pressure  on  the  fire 
box  equal  to  the  draft,  and  the  current  of  gas  and  smoke 
through  the  stack  is  stopped.  In  other  words,  smoke  is 
prevented  because  combustion  has  almost  ceased.  When 
the  engine  is  working,  the  effect  of  the  steam  jets  is  very 
slight.  The  steam  is  condensed  by  contact  with  cold  air, 
and  it  enters  the  fire  box  as  moisture,  and  its  effect  must 
be  to  lower  the  temperature  of  the  gases,  and  it  does  not 
support  combustion.  The  air  which  is  drawn  in  is  also 
cool,  and  there  is  no  real  combination  with  the  gases  until 


132  COMBUSTION   OF    COAL. 

it  is  heated  up  to  their  temperature.  From  any  point  of 
view,  according  to  the  committee  of  the  Western  Railway 
Club  on  smoke  prevention,  the  steam  and  air  jet  cannot  be 
considered  as  a  promising  device  from  which  any  success- 
ful smoke  preventer  may  be  evolved,  and  the  committee 
believe  it  to  be  important  that  this  fact  be  emphasized  for 
two  reasons :  first,  because  valuable  time  has  been  wasted 
already  in  continued  and  unsuccessful  experiments  with 
steam  jets ;  and  second,  because  their  presence  on  the 
engine  and  occasional  use  have  the  effect-  of  relieving  both 
master  mechanic  and  engineman  of  responsibility  to  a 
certain  extent.  If  the  steam  jet  is  given  up  as  hopeless, 
then  more  attention  and  effort  will  be  directed  toward 
better  proportions  of  fire  box  and  other  features  in  the 
original  construction  of  the  locomotive. 

Q.  What  is  an  econometer  ? 

The  econometer,  designed  by  Max  Arndt,  and  shown 
in  Fig.  10,  is  a  gas- weighing  machine  on  an  entirely  new 
principle,  fixed  in  an  air-tight  case  7  with  a  plate  of  glass 
in  front.  In  the  case  7  there  are  two  connecting  joints, 
39  and  40,  40  is  connected  by  a  ffi'  pipe  to  the  flue  of  the 
boiler  about  two  feet  from  the  damper,  and  39  is  con- 
nected by  a  -|"  pipe  to  an  aspirator  in  the  main  flue  be- 
tween the  damper  and  the  chimney,  or  the  chimney  itself, 
and  which  constantly  draws  a  sample  of  the  gases  from 
the  boiler  flue  through  filters,  gas  pipes,  and  balance,  dis- 
charging it  into  the  chimney.  In  the  interior  of  the 
econometer  case  7,  the  joint  40  is  connected  with  the  as- 
cending pipe  23,  and  the  joint  39  with  the  descending 
pipe  22  by  means  of  India  rubber  tubes  34  and  35. 

The  gas-weighing  machine  itself  consists  of  a  very  fine- 
ly adjusted,  highly  sensitive  balance,  to  which  is  fixed  the 


MAX   ARNDT'S    ECONOMETER. 


133 


pointer  or  index  17.  On  one  end  of  the  balance  is  sus- 
pended an  open  glass  globe  18,  with  a  capacity  of  about  a 
pint,  and  on  the  opposite  end  a  compensating  rod  32,  to 
which  is  affixed  a  scale  pan  with  a  number  of  glass  beads 
and  filings  by  which  the  gas  holder  can  be  balanced.  The 


134  COMBUSTION   OF   COAL. 

knife-edges  of  the  balance  are  steel  gilded,  and  the  caps 
are  agate.  The  whole  balance  works  on  a  pillar  screwed 
on  a  cast  plate  28.  The  latter  has  adjusting  screws  by 
which  the  balance  is  set,  both  horizontally  and  vertically. 
For  this  purpose  a  small  pendulum  is  attached  to  the  sup- 
porting pillar.  A  frame  27  is  fixed  on  the  pillar  in  which 
is  inserted  the  scale. 

The  gas-ascending  pipe  23  reaches  into  the  gas  holder 
or  weighing  globe  18,  which  has  a  neck  20  open  below 
and  surrounded  by  cup  2 1  open  above.  The  neck  20  has 
free  play  around  glass  tube  19,  as  well  as  cup  21,  so  that 
the  gas  holder  can  swing  free  from  resistance. 

The  combustion  gases,  having  to  pass  through  filters  and 
drying  chambers,  enter  the  weighing  globe  thoroughly 
cleaned  and  dried. 

As  carbonic  acid  is  about  50  per  cent  heavier  than  at- 
mospheric air  and  the  other  gases  contained  in  combustion 
gases,  so  the  gases  which  continually  fill  the  weighing 
globe  must  be  heavier  in  proportion  to  the  amount  of  car- 
bonic acid  contained  therein.  The  scale  27  is  so  divided 
that  the  movement  of  the  pointer  1 7  of  the  gas  balance 
from  one  dividing  line  to  another  corresponds  with  the 
volume  per  cent  of  CO2  in  the  gases  to  be  weighed.  The 
amount  of  carbonic  acid  in  the  gases  can  therefore  be 
read  off  at  all  times. 

Q.  What  is  the  object  of  the  econometer? 

In  Europe,  where  coal  economy  has  received  the  great- 
est attention,  it  has  long  been  the  custom  to  provide  en- 
gineers with  chemical  apparatus,  by  which  the  percentage 
of  carbonic-acid  gas  could  be  determined  at  intervals. 
This  determination,  though  irregular,  proved  of  the  great- 
est value,  and  led  to  the  invention  of  the  econometer, 


MAX  ARNDT'S  ECONOMETER.  135 

which  indicates  continuously  the  exact  percentage  of 
carbonic  acid  contained  in  the  escaping  products  of 
combustion.  The  value  of  having  a  continuous  indication, 
rather  than  one  obtained  at  infrequent  intervals,  can  hardly 
be  overestimated,  for  a  constant  guide  to  firing  is  thus 
obtained. 

In  order  to  produce  combustion,  carbon,  the  vital  ele- 
ment in  the  coal,  must  unite  with  oxygen,  which  it  does 
in  certain  unvarying  proportions.  In  the  first  stage  of 
combustion,  one  part  of  carbon  unites  with  one  part  of 
oxygen,  forming  a  combustible  gas,  known  as  carbon  mon- 
oxide, and  in  this  process  about  one-fourth  of  the  heat  is 
liberated.  In  the  second  stage,  the  carbon  monoxide  ab- 
sorbs another  part  of  oxygen,  forming  a  gas  known  as  car- 
bon dioxide  or  carbonic  acid,  and  in  this  process  the  bal- 
ance of  the  heat  is  liberated.*  As  there  is  twenty-one  per 
cent  of  oxygen  in  the  air  that  is  conveyed  to  the  carbon, 
it  is  easily  seen  that  perfect  combustion  would  produce 
twenty-one  per  cent  of  carbonic  acid,  since  all  of  the  oxy- 
gen would  unite  with  all  of  the  carbon  and  every  heat  unit 
contained  in  the  coal  would  be  liberated. 

It  is  next  to  impossible  to  obtain  perfect  combustion  in 
any  steam-boiler  furnace  for  many  reasons,  but  it  is  pos- 
sible to  obtain  and  maintain  good  combustion,  with  proper 
firing  and  correct  manipulation  of  the  draughts  and  damp- 
ers. It  is  easy  to  see  that  the  only  test  to  be  applied  is 
that  of  determining  the  percentage  of  carbonic  acid  pres- 
ent in  the  escaping  gases,  and  that  the  value  received 
from  the  burning  of  all  coal  is  in  exact  proportion  to  this 
percentage  of  gas.  Chemistry  has  determined  these 

*This  is  from  Arndt's  point  of  view.  The  generally  accepted  theory  is 
that  CO2  is  first  formed,  which  passing  up  through  the  bed  of  incandescent 
fuel  takes  up  another  equivalent  of  carbon,  resulting  in  CO. — ED. 


136  COMBUSTION    OF   COAL. 

values,  so  that  when  the  per  cent  of  carbonic  acid  is 
known,  the  value  received  from  the  burning  of  any  coal 
can  be  ascertained.  Table  13  shows  the  relative  values, 
from  which  the  difference  between  burning  coal  properly 
and  improperly  can  be  ascertained  at  a  glance. 

Q.  How  are  the  econometer  percentages  of  carbonic- 
acid  gas  affected  by  excessive  air  supply  ? 

Carbonic  acid  is  fifty  per  cent  heavier  than  air,  and  thus 
the  greater  the  percentage  contained  in  any  given  volume 
of  flue  gases  the  greater  the  weight  of  that  volume.  In 
the  econometer,  a  sample  of  the  escaping  gas  from  the 
boiler  is  drawn  continuously  through  a  balance  scale,  sus- 
pended in  air,  and  the  variations  in  weight  that  are  pro- 
duced by  the  different  states  of  combustion  are  made  to 
record  the  percentage  of  carbonic  acid.  The  weight  of 
this  gas  varies  with  the  temperature,  but  in  the  eco- 
nometer, the  sample  to  be  weighed,  and  the  air  in  which 
the  weighing  is  done,  assume  the  temperature  of  the  room, 
so  that  the  proportion  remains  exact. 

It  is  plainly  evident  that  for  each  pound  of  coal  a 
fixed  amount  of  air  is  necessary  for  combustion,  varying 
as  the  percentage  of  carbon  varies  in  the  different  coals. 
For  a  pound  of  average  quality,  about  one  hundred  and 
twenty-five  cubic  feet  of  air  is  necessary,  and  it  is  the 
inability  to  convey  this  precise  amount  to  the  furnace 
that  prevents  our  obtaining  and  maintaining  perfect  com- 
bustion. 

If  too  little  air  is  admitted,  combustion  becomes  imper- 
fect because  the  carbon  monoxide  cannot  find  the  neces- 
sary oxygen  to  complete  its  transformation  into  carbon 
dioxide,  and  this  is  the  most  wasteful  condition  of  firing, 
for  the  largest  part  of  the  heat  is  given  off  in  the  second 


LOSS   BY    IMPERFECT   COMBUSTION. 


137 


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If  the  Econometer 
shows  

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And  the  loss  of  fuel 
at  518°  Fahr. 
amounts  to  

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sSsaaAB  jo  |BOD  JOjj 

138  COMBUSTION    OF   COAL. 

stage  of  combustion.  *  This  case  is  seldom  met  with  in 
practice,  for  most  boiler  furnaces  are  supplied  with  too 
much  air.  Then  the  combustion  is  poor  because  there  is 
a  large  amount  of  air  passing  through  the  fire,  the  oxygen 
of  which  cannot  be  consumed.  This  surplus  air  must  be 
heated  to  the  same  temperature  as  the  escaping  gases, 
thereby  absorbing  the  heat  already  generated,  which 
should  pass  instead  into  the  water  contained  in  the  boiler. 

Q.  In  what  manner  may  loss  of  fuel  through  imperfect 
furnace  detail  or  management  be  detected  by  the  econom- 

eter? 

j 

Loss  of  fuel  calculated  and  shown  in  Table  1 3  can  be 
caused  in  a  variety  of  ways,  and  is  to  be  sought  for  in  all 
of  the  accessories  of  the  furnace.  It  may  result  from  an 
excessive  or  defective  draft,  from  faulty  grates  or  wrong 
proportion  of  grate  surface,  there  may  be  defects  in  the 
boiler  setting  or  in  the  fire  and  ash-pit  doors,  that  should 
be  remedied.  The  proper  thickness  of  fire  is  something 
that  must  be  determined,  varying  as  it  does  with  the  many 
different  conditions  surrounding  all  steam  plants. 

By  first  obtaining  the  percentage  of  carbonic  acid  in  the 
gases  produced  with  ordinary  firing  and  then  experiment- 
ing with  the  boiler  in  connection  with  the  econometer,  any 
fireman  can  soon  ascertain  the  proper  thickness  of  fire  and 
draft  necessary  to  insure  good  combustion.  If  with  a 
high  percentage  of  carbonic  acid  the  gauges  should  show 
too  much  steam,  a  case  often  experienced  in  practice,  it  is 
evident  that  the  grate  surface  should  be  reduced,  which 
can  be  done  by  bricking  up  at  the  back  end  of  the  ashpit, 
or  at  the  back  end  or  sides  of  grates  over  the  bars. 

A  very  common  source  of  waste  is  the  formation  of 

*  See  foot  note  on  page  135. 


LOSS   BY   IMPERFECT   COMBUSTION.  139 

holes  in  the  fire,  and  of  the  presence  of  these,  the  econo- 
meter  is  a  never-failing  indicator.  By  drawing  samples 
of  gas  from  the  entrance  and  exit  of  the  flues,  and  com- 
paring the  percentage  of  carbonic  acid,  any  existing  de- 
fects in  the  setting  and  brickwork  will  be  discovered. 


CHAPTER  VI. 

HEAT    DEVELOPED    BY    COMBUSTION. 

Q.  What  is  heat? 

In  steam  engineering  heat  is  regarded  from  the  dynam- 
ical or  mechanical  theory  only,  on  the  supposition  that 
heat  and  mechanical  force  are  convertible  one  into  the 
other.  From  the  great  number  of  experiments  in  the  gen- 
eration of  heat  by  mechanical  processes,  by  friction,  by 
the  arrest  of  motion,  either  gradually  or  by  percussion,  by 
the  change  in  the  quantity  of  heat  observed  in  the  case  of 
expansion,  etc.,  has  led  investigators  to  the  conclusion  that 
heat  is  simply  a  motion  of  ultimate  particles,  and  that  the 
molecular  structure  of  bodies  has  much  to  do  with  their  ca- 
pacities for  heat ;  and  an  increase  or  decrease  of  tempera- 
ture is  simply  an  increase  or  decrease  of  molecular  motion. 

Q.  What  numerical  value,  in  heat  units,  should  be 
used  in  estimating  the  calorific  power  of  carbon  in  con- 
nection with  coal  analysis  ? 

Carefully  conducted  experiments  by  the  earlier  as  well 
as  the  more  recent  investigators  have  yielded  practically 
the  same  results.  Three  numerical  values  for  carbon  are 
in  common  use,  viz.,  14,544,  14,540,  14,500  heat  units. 
These  are  so  nearly  alike  as  to  cause  no  confusion,  and 
practically  no  error  in  any  calculations  relating  to  the 
calorific  value  of  fuel.  The  latter  is  the  one  in  very  gen- 
eral use. 


HEAT   GENERATED    BY    COMBUSTION.  141 

In  the  examples  given  in  this  book  the  writer  has  fol- 
lowed as  nearly  as  possible  the  numerical  values  given  by 
investigators,  those  used  in  geological  reports,  and  in  any 
correspondence  relating  to  the  coal  then  under  considera- 
tion. 

Q.  What  quantity  of  heat  is  generated  by  the  con- 
version of  carbonic  oxide,  CO,  into  carbonic-acid  gas,  C02  ? 

Calorimeter  tests  show  that  one  pound  of  carbonic  oxide 
burnt  to  carbonic-acid  gas  develops  4,325  heat  units. 

It  will  be  seen  that  a  loss  of  heat  occurs  even  though  all 
the  carbonic  oxide  in  the  furnace  be  converted  into  car- 
bonic-acid gas,  because  the  chemical  union  which  produces 
the  latter  gas  yields  14,500  heat  units,  whereas  burning 
carbon  to  carbonic  oxide  yields  only  4,450  heat  units,  and 
the  burning  of  CO  into  CO2  yields  4,325  heat  units,  or  a 
total  of  8,775  neat  units.  This  is  5,725  heat  units  per 
pound  less  than  the  direct  conversion  of  carbon  into  car- 
bonic-acid gas,  a  loss  of  39  per  cent. 

Q.  Can  the  loss  of  heat  occasioned  by  burning  carbon 
to  carbonic  oxide,  CO,  be  recovered  by  its  subsequent  con- 
version into  carbonic-acid  gas,  C02,  before  it  leaves  the 
furnace  ? 

The  burning  of  carbonic  oxide,  CO,  in  the  combustion 
chamber  above  the  fire  is  a  wholly  distinct  operation  from 
the  combustion  of  the  coal  on  the  grates,  one  result  of 
which  is  the  formation  of  the  CO. 

There  are  two  methods  by  which  this  conversion  from 
CO  to  CO,  may  be  accomplished :  first,  by  the  admission 
of  surplus  air  through  the  bed  of  incandescent  fuel ;  sec- 
ond, by  the  admission  of  air  through  perforations  in  the 
lining  of  the  fire  door,  through  the  side  walls  of  the  fur- 


142  COMBUSTION   OF    COAL. 

nace,  through  a  perforated  pipe  in  the  furnace,  through 
perforations  in  or  adjoining  the  bridge  wall.  All  of  the 
above  connect  in  some  manner  with  the  atmosphere. 
Shortening  the  grates  so  as  to  leave  a  space  at  the  end  to 
allow  passage  of  air  between  the  grates  and  the  bridge 
wall.  All  of  these  methods  have  been  tried  with  more  or 
less  success  depending  upon  local  conditions. 

Q.  Upon  what  is  the  temperature   of  fire   conditioned? 

The  temperature  of  combustion  is  conditioned  upon  the 
nature  of  the  fuel  burned ;  the  nature  of  the  products  of 
combustion ;  the  quantity  of  the  products  of  combustion ; 
the  specific  heat  of  the  gases  present  in  the  furnace  result- 
ing from  combustion,  including  the  quantity  of  air  present 
at  the  moment  of  combustion  in  order  to  render  it  com- 
plete. 

Q.  How  may  the  temperature  of  the  combustion  of 
carbon  be  estimated  ? 

In  the  complete  combustion  of  one  pound  of  carbon  we 
have: 

Carbon I 

Oxygen 2.67 

3-67 

pounds  of  carbonic-acid  gas. 

In  addition  thereto  we  have  8.94  pounds  of  nitrogen  left 
after  the  separation  of  the  oxygen  from  the  atmospheric  air. 
The  specific  heat  of  carbonic-acid  gas  is  0.216,  and  that 
of  nitrogen  0.244.     We  have  then  : 

Specific         Heat 
Products-  Pounds-      heat.  units. 

Carbonic-acid  gas 3.67  X  .216  =    .794 

Nitrogen 8.94  X  .244  =  2. 181 

Total..  2.975 


TEMPERATURE   OF   COMBUSTION.  143 

heat  units  absorbed  in  raising  the  temperature  of  the  prod- 
ucts of  combustion  of  one  pound  of  carbon,  i  °  F. 

The  combined  weight  of  the  two  products  are  3.67  -f- 

Heatunits2.975 

8.94=  12.61  pounds.      Then:  ^ j—         — ^-  =0.236, 

Pounds        1 2.6 1 

their  mean  specific  heat. 

The  total  heat  of  the  combustion  of  one  pound  of  car- 
bon in  oxygen  gas  is  14,544  heat  units;  divide  this  by  the 

2.975  heat  units  absorbed,  we  have:         — —  =  4889°  F. 

as  the  highest  theoretical  temperature  attainable  by 
the  complete  combustion  of  one  pound  of  carbon,  using 
1 1. 6 1  pounds  of  air  per  pound  of  carbon,  the  minimum 
theoretical  limit. 

Example  2.  Suppose  that  eighteen  pounds  of  air  are  used 
instead  of  the  theoretical  quantity  given  above,  and  that  the 
combustion  is  complete,  we  then  have 

Carbon I 

Oxygen / 2.67 

Nitrogen 8. 94 

Surplus  air 6. 39 

19.00 

pounds  of  furnace  products. 

The  specific  heat  of  air  is  0.237,  proceeding  as  before: 

Specific          Heat 
Products.  Pounds. 

heat.  units. 

Carbonic-acid  gas 3. 67  X  .  216  =    .  794 

Nitrogen 8.94  X  .244  =  2.181 

Air,  uncombined  . .    6. 39  X  .  237  =  1.519 


Totals  ............................    1  9.  oo  4.  494 

4  4Q4  14 

Then  :  -  =  0.237,  the  mean  specific  heat. 


19  4.494 

3236°    F.,  the  temperature  of  the  fire  under  the  above 
conditions.     It  will  be  noted  that  a  reduction  of  1653°  F. 


144 


COMBUSTION   OF   COAL. 


occurs  through  the  admission  of  50  per  cent  more  air  than 
was  needed  for  combustion.  Had  double  the  quantity  of 
air  passed  through  the  fire,  the  temperature  would  be 
about  2450°  F. 

TABLE  14. — WEIGHT  AND  SPECIFIC  HEAT  OF  THE  PRODUCTS  OF  COM- 
BUSTION, AND  THE  TEMPERATURE  OF  COMBUSTION. 

(From  D.  K.  Clark's  Rules,  Tables,  and  Data.) 


One  pound  of  combustible. 

GASEOUS  PRODUCTS    FOR  ONE  POUND    OF  COM- 
BUSTIBLE. 

Weight. 

Mean 
specific 
heat. 

Heat  to 
raise 
tempera- 
ture i°  F. 

Temperature  of 
combustion. 

Pounds. 
35.8 

15-9 
11.94 

12.6 

10.09 
18.4 
5-35 
22.64 

Water  =  i. 
.302 

.257 
.246 
.236 
.270 
.268 
.211 
.242 

Units. 
10.814 
4.089 
2-935 
2.973 
2.680 

4-933 
I.I28 
5.478 

Deg.  P. 
5744 
5219 
4879 
4877 
4825 
4766 

3575 
2614 

Ratio. 
100 
91 

85 
85 
84 
83 
62 

45 

Olefiant  gas  

Coal  (average) 

Carbon    or  pure  coke 

Alcohol.  . 

Light  carburetted  hydrogen..  .  . 
Sulphur                                   .... 

Coal,  with  double  supply  of  air. 

Q.  How  may  the  quantity  of  heat  developed  by  com- 
bustion be  determined? 

The  heat  developed  by  chemical  action  or  combustion 
is  best  determined  by  the  use  of  an  apparatus  known  as  a 
calorimeter,  by  means  of  which  a  combustible  is  burnt  in 
oxygen  gas,  the  heat  liberated  by  combustion  being  ab- 
sorbed by  the  water  which  surrounds  the  combustion 
chamber.  The  weight  of  combustible,  the  oxygen,  and 
the  water  being  known,  the  quantity  of  heat  evolved  by 
the  combustion  of  each  substance  can  easily  be  calculated 
by  the  rise  in  temperature  of  the  water. 

The  apparatus  used  by  Favre  and  Silberman  for  meas- 
uring the  heat  evolved  by  the  combustion  of  various  sub- 


FAVRE  AND   SILBERMANN'S   CALORIMETER.         145 


stances  in  oxygen  gas  is  represented,  with  the  omission  of 
minor  details,  in  Fig.  n,  in  which  C  is  a  vessel  of  gilt 
brass  plate,  immersed  in  a  water  calorimeter,  A  A,  of  sil- 
vered copper  plate,  and  the  latter  is  enclosed  in  an  outer 
vessel,  B  B,  the  space  between  A  and  B  being  filled  with 
swandown  to  prevent  the  escape  of  heat  from  the  water 
A.  The  vessels  A  and  B  are 
closed  with  lids  having  aper- 
tures for  the  insertion  of  tubes 
and  thermometers.  The  com- 
bustions are  performed  in  the 
vessel  C,  into  which  oxygen  is 
introduced  through  the  tube 
c  d,  and  the  gaseous  products 
of  the  combustion  escape  by 
the  tube,  e  f  g  //,  the  lower 
part  of  which  is  bent  in  nu- 
merous coils,  to  facilitate  as 
much  as  possible  the  trans- 
mission of  the  heat  of  these 
gases  to  the  water  in  the  cal- 
orimeter. The  extremity,  h, 
of  this  tube  is  connected  with 

a  gasometer  or  with  an  absorbing  apparatus.  To  insure 
uniformity  of  temperature  in  the  water,  a  flat  ring  of  metal, 
i  /',  is  moved  up  and  down  by  means  of  the  rod  Ki.  Com- 
bustible gases  were  introduced  into  the  vessel  C,  by  means 
of  fine  tubes,  the  gas  being  previously  set  on  fire  at  the 
aperture.  Solid  bodies  were  attached  to  fine  platinum 
wires  suspended  from  the  lid  of  the  calorimeter.  The  liq- 
uids were  burned  in  small  capsules  or  in  lamps  with 
asbestos  wicks.  Charcoal  was  disposed  in  a  layer  on  a 
sieve-formed  bottom,  through  the  openings  of  which  the 
10 


FIG.  n. 


146 


COMBUSTION    OF    COAL. 


oxygen  had  access  to  it.  The  heat  evolved  was  measured 
by  the  rise  of  temperature  of  the  known  quantity  of  water 
in  the  calorimeter. 

TABLE  15. — QUANTITIES  OF   HEAT   EVOLVED  BY  THE  COMBUSTION  OF 
ONE  POUND  OF  COMBUSTIBLE  WITH  OXYGEN.    (Favre  and  Silberman) . 


Substances. 

Formula. 

Product. 

British 
thermal  units. 

Gases  : 
Hydrogen  . 

II 

Ha  O 

62  032 

Carbonic  oxide  . 

CO 

CO2      . 

4  12=1 

Marsh  gas  

CH4  . 

CO2  and  H2  O 

27  Sia 

Olefiant  gas  

Ca  H4 

CO2  and  H2  O 

21   1AT, 

Liquids  : 
Oil  of  turpentine  
Alcohol  .          .... 

C]0    H]6    .... 

C2  H6  O 

CO2  and  H2  O 
CO2  and  H2  O 

19-533 

12  cni 

Spermaceti  (solid)  
Sulphate  of  carbon  

C32H6402.. 
CS2    .... 

CO2  and  H2  O 
CO2  and  SO2 

18,616 

6  122 

Solids  : 
Carbon  (wood  charcoal  )  

c  j 

CO  
CO2  

4,451 
14,544 

Gas  coke 

14  48=^ 

Graphite  from  blast  furnaces  . 

13  Q72 

Native  graphite                   .... 

14,035 

Sulphur  (  native) 

s 

SO* 

4OJ.8 

Phosphorus  (by  Andrews)  .... 

p  

P2  05  

10,715 

Q.  What  are  the  relations  between  quantity  of  heat 
and  temperature  developed  in  combustion  ? 

The  actual  amount  of  heat  given  out  during  the  com- 
plete oxidation  of  any  substance  is  the  same  whether  the 
combination  is  slow  or  rapid,  and  is  carried  on  in  air  or  in 
oxygen.  But  it  is  quite  different  in  regard  to  the  temper- 
ature developed,  this  depending  on  the  concentration  of 
the  heat ;  and  so  being  higher,  the  more  rapid  the  com- 
bustion and  the  less  extraneous  matter  is  present  to  absorb 
the  heat.  The  temperature  of  a  hydrogen  or  a  coal-gas 
flame  burning  in  oxygen  is  very  much  higher  than  that  of 
a  similar  flame  burning  in  air. 


HEAT 
UNITS 


WASTED,  USED  IN  EIRING  UP,  LEFT  .IN  BOX,  STANDING 
IDLE  ETC. 


LOST  IN  HEATED  AIR,  GASES  AND  VAPOR c. 


EVAPORATING  MOISTURE  IN  COAL 

HEATING  COAL  TO  IGNITION     -- 

HEAT  AND  UNCONSUMED  COAL  IN  ASHES 


UNCONSUVED  GASES 


LOST  IN  "SPARKS" 


RADIATION   FROM  BOILER,    FIRE  BOX  ETC. 

HEAT   LOST  IN   ENTRAINED  WATER  .23  LB8. 


HEATING  FEED  WATER  (55    TO  212°) 


LATENT   HEAT  AT  361  (OF  SEPARATION  ONLY 
77B.8  H.U. 


FRICTION  IN  PORTS,  STEAM  PASSAGES-ETC.-.. 

CLEARANCE    --  ^ 

CYLINDER  CONDENSATION     —  "*•*• 

BACK  PRESSURE  ABOVE  ATMOSPHERE "f 

BACK  PRESSURE  BELOW  ATMOSPHERE" - 
PER  COMPRESSION    --  .--2.8--- 

LOST  EFFECTIVE  WORK  BY  INCOMPLETE  EXPANSION    ! 
IN  CYL.    ETC.  i 

MACHINERY  FRICTION  AND  HEAD  RESISTANCE- -42i-9 •-. 

TRACTION  OF  ENGINE     --  69r5' "  '  "  1 - 

TRACTION  OF  CARS ~~~ 

TRACTION  OF  LOAD  (NET  USEFUL  EFFECtT. 


ASSUMED  AT 


50$  IN  EXCESS  OF  THEORETICAL.AMO.UNT, 

(9.  LBS.    AIR  PER  LB.    COAL) 


ESTIMATED  AVERAGE. 

\ THO8.   BOX. 

-  -2%   EXCLUDING  "WASTE" 


>__KENT   L088  2$  TO  30$.   LOVELL'S 
EXPERIMENTS  N.P.  RY.  1896,    18$. 


--5$  ASSUMED,    EXCLUDING  WASTE. 

ASSUMED  AT  5$  OF  APPARENT 
" "EVAPORATION 

--(BOILER  EFFICIENCY  51. 79^, LOSSES 
48.21*) 


_ (MEAN  EVAPORATION  4.66  LBS.  WATER 
LESS  5$  PRIMAGE,   MEAN  OF  FIVE  TESTS) 


DROP  IN  PRESSURE  FROM  BOILER  TO  CYL. 
/MO*  TO  125* 

/.RATIO     EXPANSION  1.83,  CLEARANCE  7jf, 
' /  COMPRESSION  3M$ 
'   , 'ACTUAL 

',  '8  LBS.  ABOVE  ATMOSPHERE 
',--14.7   LBS.  ABSOLUTE 
--MOF  CLEARANCE 

-_*INCLUDE8  EXPANSION  AGAINST 

ATMOSPHERE 

:;-  ASSUMED  AT  10$  NET  EFFECTIVE 

-  -   I?,TON8  ^i  °F  TOTAL.' PRESSURE  ON 

-T98  «  &  :.    "  ;PI8THONU;428 


*  This  item  includes  errors  of  assumption  .as  follows:  That  expansion  is  hyper- 
bolic, that  latent  heat  of  separation  is  a  constant  at  all  temperatures,  and  that  mo 
latent  heat  (of  separation)  is  transformed  into  work.  The  net  .error  probably 
does  not  exceed  25  h.  n. 

Where  the  Coal  Goes  When  Burned  in  a  Locomotive  Firebox. 
FIG.  12. 


148  COMBUSTION   OF  COAL. 

Q.  What  is  the  heating  power  of  sulphur  contained  in  coal  ? 

The  quantity  of  sulphur  in  good  coal  is  so  small  that  its 
calorific  value  is  commonly  neglected  in  any  calculations 
relating  to  the  heating  power  of  coal. 

The  quantity  of  heat  evolved  in  the  complete  combus- 
tion of  one  pound  of  sulphur  in  oxygen  gas,  as  determined 
by  Favre  and  Silberman,  is  4,048  heat  units.  The  equiva- 
lent evaporation  from  and  at  212°  F.  would  be  4048  -h  966 
=  4.19  pounds  of  water  per  pound  of  sulphur.  The  tem- 
perature of  the  combustion  of  sulphur  is  about  3575°  F. 

Q.  How  is  the  heat  evolved  from  coal  distributed  in 
locomotive  practice? 

The  accompanying  diagram  (Fig.  12),  by  E.  H.  Mc- 
Henry,  chief  engineer  Northern  Pacific  Railway,  shows 
heat  losses  and  net  effective  work  of  one  pound  of  Red 
Lodge  coal  burned  in  a  typical  Mogul  engine,  in  ordinary 
service,  Northern  Pacific  Railway. 

Mogul  engine;  Class  D2 ;  cyl.,  i8y&  in.  by  24  in.; 
boiler  pressure,  140  pounds;  cut  off,  I2f  in.;  ind.  h.  p., 
381  ;  speed,  16  miles  an  hour;  weight  of  engine  and  train, 
550  tons.  Red  Lodge  coal  (by  analysis),  10,000  heat 
units  per  pound. 

i  pound  coal  =  o.  168  h.  p.  hour. 
5.95  pounds  coal  per  h.  p.  hour. 
27.73  pounds  water  per  h.  p.  hour. 

f  5 1   per  cent  of  the  theoretically  available 

heat  in  the  steam  by  a  non-condensing 
of  the  train          engine 

,   36.2  per  cent  of  the  theoretically  available 
heat  in  the  steam  by  a  condensing  engine. 

on     l  n  t '       7.4  per  cent  of  the  total  heat  in  the  steam, 
work  of  but      3  8  per  cent  of  the  total  heat  in  the  coaL 


CHEMICAL   CHANGES.  149 

The  chart  was  compiled  from  actual  tests  of  a  Mogul 
engine  on  the  Yellowstone  Division  of  the  Northern  Pa- 
cific Railway,  in  which  the  coal  was  weighed  and  the 
water  measured,  frequent  indicator  cards  taken,  and  the 
final  net  effective  traction  at  the  periphery  of  the  drivers 
determined  by  a  dynamometer,  thus  affording  an  opportu- 
nity of  checking  the  calculations  at  several  points  in  the 
length  of  the  column,  with  the  effect  of  localizing  minor 
errors.  The  efficiency  of  some  modern  engines  is  consid- 
erably higher  than  that  shown,  but  the  chart  will  closely 
apply  to  the  great  majority  of  the  engines  in  present  ser- 
vice all  over  the  United  States. 

Q.  Is  heat  generated  by  chemical  action  convertible  into 
mechanical  energy  ? 

Chemical  changes  are  either  atomic  or  molecular,  and 
all  differences  in  the  temperature  of  bodies  are  due  to  the 
changes  in  their  molecular  condition ;  therefore,  chemical 
action,  heat,  and  mechanical  energy  should  be  mutually 
convertible.  Chemical  changes  are  always  attended  by  a 
change  in  the  thermal  conditions  of  the  bodies  acted  upon, 
in  which  combinations  as  a  rule  produce  heat,  while  de- 
compositions produce  cold  or  a  disappearance  of  heat. 
The  amount  of  heat  any  particular  body  is  capable  of  giv- 
ing off  must  be  determined  as  yet  experimentally.  The 
researches  of  Favre  and  Silberman,  Andrews,  Thompson, 
Joule,  and  others,  have  given  us  a  very  close  approxima- 
tion to  the  dynamic  value  of  heat  and  the  heating  power 
of  different  fuels. 

Q.  What  is  the  effect  of  heat  upon  water? 

Water  within  the  range  of  its  solidifying  point  and  that 
at  which  it  becomes  an  elastic  vapor  is  subject  to  very 
great  irregularities.  If  water  be  taken  in  a  solid  state,  or 


COMBUSTION    OF   COAL. 


at  a  temperature  of  32°  F.  before  it  has  solidified,  and 
heat  be  communicated  to  it,  instead  of  expanding,  it  act- 
ually contracts  until  it  marks  about  39.4°  F.,  at  which  it 
has  attained  its  greatest  density.  Above  this  it  expands 
in  the  same  ratio  that  the  contraction  took  place  for  an 
equal  number  of  degrees,  but  beyond  that  point  it  obeys 
the  general  law. 

Q.  What  is  the  effect  of  heat  upon  gases? 

All  gases  at  ordinary  temperatures  are  in  a  state  in 
which  the  atomical  aggregation  manifests  a  highly  repul- 
sive tendency.  It  is  evident,  therefore,  that  gases  will  be 
influenced  to  a  greater  extent  by  heat  than  either  solids  or 
liquids. 

A  remarkable  coincidence  or  uniformity  exists  among 
the  different  gases ;  and  knowing  the  rate  of  expansion  of 
one,  the  same  may  be  taken  as  the  expansive  power  of  the 
other  permanent  gases  when  subjected  to  an  equal  increase 
of  temperature.  It  was  found,  however,  by  Magnus  and 
Regnault,  that  the  operation  of  this  law  is  not  perfectly 
uniform,  especially  with  reference  to  the  easily  liquefied 
gases,  which  are  more  expansible  than  air  when  exposed  to 
equal  increments  of  heat,  as  the  following  table  will  show : 

TABLE  16. — EXPANSION  OF  GASES  BETWEEN  32°  AND  212°  FAHR. 


Gases. 

Constant 
volume. 

Constant 
pressure. 

Air                                                     

0.3665 

0.3670 

Nitrogen                     .  .          

0.3668 

Hydrogen  

0.3667 

0.3661 

o.  3667 

o.  3669 

Carbonic  acid                               

0.3688 

O.37IO 

Nitrous  oxide                              

0.3676 

0.3720 

Cyanogen               .        

0.3829 

0.3877 

0.3845 

o  .  3903 

UNITS   OF   HEAT.  15  I 

A  sensible  increase  in  the  rate  of  expansion  is  also 
found  when  the  gas  is  submitted  to  pressure,  compared 
with  that  which  takes  place  when  it  is  in  a  rarefied  state. 
The  expansion  of  perfect  gases  has  been  employed  in  the 
enunciation  and  perfecting  of  a  new  scale  of  temperature, 
known  as  the  absolute  scale  of  temperature. 

Q.  What  is  the  rate  of  expansion  of  air  by  the  appli- 
cation of  heat  ? 

By  former  investigations  this  was  found  to  amount  to 
about  375  parts  in  1,000  of  air  when  heated  from  the 
freezing  to  the  boiling  point  of  water.  Later  researches, 
however,  have  shown  that  the  true  expansion  of  air  within 

these  limits  is  365  parts,  or  . of  the  whole  for  each 

493-2 

degree  of  the  Fahrenheit  scale.  Below  the  freezing  and 
above  the  boiling  point  of  water  the  expansion  is  in  the 
same  ratio. 

Q.  What  is  the  British  thermal  unit  ? 

A  British  thermal  unit  is  that  quantity  of  heat  neces- 
sary to  raise  the  temperature  of  one  pound  of  water  from 
39°  to  40°  F.,  the  former  being  the  temperature  of  its 
greatest  density.  This  is  equivalent  to  772  foot-pounds. 

Q.  What  is  a  calorie  ? 

A  calorie  is  the  metric  unit  of  heat.  It  is  that  quantity 
of  heat  required  to  raise  one  gram  of  water  from  4°  to  5° 
C.  Some  writers  give  the  range  of  temperature  from  o° 
to  i°  C. ,  which  is  in  error,  as  the  greatest  density  of 
water  occurs  at  3.94°  C.,  or  39.4°  F. 

i  calorie  =  3.968  British  thermal  units. 

i  British  thermal  unit  =  .252  calorie. 


152  COMBUSTION   OF   COAL. 

Q.  What  is  the  relation  of  atomic  weights  to  specific 
heat? 

In  regard  to  the  atomic  weights  and  their  relation  to 
specific  heat,  it  is  a  noteworthy  fact  that  as  the  specific 
heat  increases  the  atomic  weight  diminishes,  and  vice 
versa  ;  so  that  the  product  of  the  atomic  weight  and  spe- 
cific heat  is,  in  almost  all  cases,  a  sensible  constant  quan- 
tity. For  equal  weights  the  specific  heat  of  the  several 
gases  entering  into  the  problem  of  coal  combustion  ought 
to  bear  a  direct  relation  to  each  other,  for  example : 

The  specific  heat,  for  equal  weights,  of  the  following 
gases,  were  found  by  Regnault  to  be :  k 

Air,          specific  heat  for  equal  weight o.  237 

Oxygen         "         "  0.218 

Nitrogen      "         "  "        o.  244 

Hydrogen    "         "  "        3-4°9 

On  the  supposition  that,  for  equal  volumes,  gases  con- 
tain the  same  number  of  atoms,  we  should  expect  the  gases 
oxygen  and  nitrogen,  as  well  as  the  mixture' of  the  two  lat- 
ter to  form  air,  to  have  the  specific  heat  of  each  practically 
equal,  according  to  their  atomic  weights.  The  atomic 
weight  of  hydrogen  is  i,  and  its  specific  heat  is  3.409. 
We  should  then  expect : 

3.409  -r-  14  =  0.243,  specific  heat  nitrogen,  N  14. 
3.409  -j-  16  =  0.213,        "         "     oxygen,  O  16. 

0.237,       "         "     23$  O  16,  77$  N  16  =  air. 

A  result  which  experimentally  verifies  the  above  con- 
clusion so  far  as  these  two  gases  are  concerned. 

The  temperatures  at  which  determinations  were  made 
were:  Carbon,  980°  C. ;  sodium,  —34°  to +  7°  C. ;  sili- 
con, 232°  C. ;  phosphorus,  —78°  to  +  10°  C.;  potassium, 
—78°  to+  10°  C. ;  mercury,  —78°  to  —40°  C.  For  all 


SPECIFIC    HEATS    OF    SOLIDS. 


153 


the  other  elements  the  determinations  were  made  some- 
where between  o°  and  100°  C.  The  numbers  in  these 
cases  may  be  regarded  as  approximately  representing  the 
mean  specific  heats  for  the  temperature  interval,  40°  to 
60°  C. 

TABLE  17. — SPECIFIC  HEATS  OF  THE  SOLID  ELEMENTS. 


Element. 

Specific  heat. 

Atomic 
weight. 

Specific  heat 
X  atomic 
weight. 

Observer. 

Carbon 

46^ 

II  Q7 

e.c 

Weber. 

Sodium 

2QT 

2"? 

6.7 

Regnault. 

Magnesium 

2^ 

24 

6 

Aluminum  . 

214 

27.O2 

5.8 

(i 

Silicon    .                     ... 

2O3 

28 

5.7 

Weber. 

Phosphorus  

174 

3O.Q6 

5-4 

Regnault. 

Sulphur        .        

.178 

3I.Q8 

5-7 

Potassium  

.166 

3Q.O4 

6.5 

« 

Calcium   

.I7O 

30-Q 

6.8 

Bunsen. 

Manganese    

.122 

55 

6.7 

Regnault. 

Iron 

114 

ce  Q 

6-4 

Nickel 

108 

58.6 

6.3 

n 

CooDer 

oos 

63  4 

6.1 

M 

Zinc 

005 

64.0 

6.2 

« 

Silver 

.057 

107.66 

6.1 

14 

Tin                       

.0562 

II7.8 

6.6 

«< 

Antimony  

.0508 

1  2O 

6.0 

" 

Platinum  

.0324 

IQ5 

6-3 

II 

Gold  

.0324 

107 

6.4 

«< 

Mercury  (solid) 

O3IQ 

IQQ  8 

6.4 

II 

Lead.    . 

0^07 

206.4 

6.3 

« 

Bismuth. 

0^08 

208 

6.3 

« 

Q.  What  is  the  specific  heat  of  water? 

Water  exists  in  three  states — solid,  liquid,  gaseous  or 
steam.  The  specific  heats  of  each  are  as  follows :  Ice, 
0.504;  water,  i.ooo;  gaseous  steam,  0.622. 

Q.  What  is  meant  by  conduction  of  heat? 

This  property  of  hea't,  although  by  many  supposed  to 
be  due  to  radiation,  owing  to  the  particles  of  matter  not 


154  COMBUSTION   OF   COAL. 

being  in  absolute  contact,  is,  however,  generally  acknowl- 
edged to  be  due  to  a  distinct  action,  that  of  conduction. 
Dense  and  heavy  substances  are  generally  good  conduc- 
tors ;  light  and  porous  bodies  have  this  property  only 
imperfectly. 

TABLE  18. — THERMAL  CONDUCTIVITY  OF  METALS. 

Silver 100.  o 

Copper 73.6 

Gold 53.2 

Brass 23.6 

Tin 14. 5 

Iron 11.9 

Lead 8.5 

Platinum ...  6. 4 

German  Silver 6. 3 

Bismuth 1.8 

Liquids  in  general  are  bad  conductors  of  heat ;  but  liquids 
do  conduct  heat  in  some  measure,  subject  to  the  same  laws 
as  solids,  although  as  regards  water  and  other  such  mobile 
liquids,  very  feebly. 

Q.  Do  all  bodies  conduct  heat  alike? 

They  do  not.  Good  conductors  are  those  bodies  in 
which  any  inequality  of  temperature  is  quickly  equalized, 
the  excess  of  heat  being  transmitted  with  great  prompti- 
tude and  facility  from  particle  to  particle.  The  metals  in 
general  are  good  conductors,  but  different  metals  have  dif- 
ferent degrees  of  conductivity. 

Imperfect  conductors  are  those  bodies  in  which  the  heat 
passes  more  slowly  and  imperfectly  through  the  dimensions 
of  a  body,  and  in  which,  therefore,  the  equilibrium  of  tem- 
perature is  more  slowly  established. 

Non-conductors  are  bodies  in  which  the  excess  of  heat 
fails  to  be  transmitted  from  particle  to  particle  before  it 


CONVECTION    OF    HEAT.  155 

has  been  dissipated  in  other  ways.     Earths  and  woods  are 
bad  conductors,  and  soft  or  spongy  substances  still  worse. 

Q.  What  is  meant  by  convection  of  heat? 

Convection  means  to  carry  or  to  convey.  As  applied  to 
the  transfer  of  heat  to  liquids  and  gases  it  means  the  car- 
rying or  conveying  of  heat  from  one  particle  to  another  by 
an  actual  movement  of  each  heated  particle  among  those 
of  lower  temperature,  and  as  each  colder  particle  with 
which  the  heated  particle  comes  in  contact  takes  up  a  por- 
tion of  the  heat,  the  movement  of  all  the  particles  will 
continue  until  all  are  of  equal  temperature. 

Q.  What  is  the  practical  or  useful  effect  of  the  convec- 
tion of  heat  in  furnace  gases? 

The  application  of  currents  of  heated  air  is  of  great 
practical  importance;  for  example,  the  heat  derived  from 
the  combustion  of  coal  on  the  grate  expands  the  air  and 
gases  in  the  furnace  and  causes  their  ascent  up  the  chim- 
ney, while  an  influx  of  air  to  the  fire,  through  the  ash  pit, 
takes  its  place.  The  force  of  the  current  or  draft  thus 
formed  will  be  in  proportion  to  the  greater  expansion  of  a 
column  of  air  of  the  height  of  the  chimney  than  that  of  an 
equal  column  externally.  Common  air  like  other  gases 
increases  nearly  ^^  of  its  bulk  for  each  degree  Fahrenheit. 
Hence  by  ascertaining  the  internal  temperature  and  height 
of  the  chimney  the  force  of  the  draft  may  be  calculated. 

Q.  How  do  gases  conduct  heat? 

Gases  resemble  liquids  in  their  mode  of  conducting  heat 
— that  is  to  say,  their  power  of  actual  conduction  is  inap- 
preciable;  but  by  their  property  of  convection  currents  are 
instituted  by  which  the  heat  is  disseminated  throughout  the 


156  COMBUSTION   OF   COAL. 

mass.  To  observe  this,  hold  the  hand  by  the  side  of  a 
lighted  candle  and  then  at  the  same  distance  above  it. 
Little  heat  is  received  by  the  hand  in  its  first  position, 
while  in  the  second  the  increase  of  temperature  is  immedi- 
ately obvious,  the  greater  portion  of  the  heat  being  carried 
off  by  the  ascending  current,  which  in  gases  is  more  active 
than  in  liquids,  owing  to  their  power  of  expansion  being 
so  much  greater. 

Q.  What  is  radiation  of  heat? 

When  heat  emanates,  or  is  thrown  off  by  a  body,  as  from 
a  bar  of  hot  iron,  heat  is  said  to  be  radiated  from  it,  and 
is  denominated  radiant  heat.  The  rate  of  cooling  expresses 
the  radiating  power ;  and  the  radiating  power  of  bodies  is 
more  influenced  by  the  state  of  their  surface  than  by  the 
nature  of  the  material.  Bright  or  polished  surfaces  radi- 
ate heat  much  more  slowly  than  rough  or  black  ones. 

Q.  What  is  meant  by  the  term  latent  heat? 

Latent  heat  is  the  quantity  of  heat  which  must  be  com- 
municated to  a  body  in  a  given  state  in  order  to  convert 
it  into  another  state  without  changing  its  temperature ;  or, 
to  put  it  in  another  form,  it  is  that  quantity  of  heat  which 
disappears,  or  becomes  concealed  in  a  body,  .while  produc- 
ing some  change  in  it  other  than  a  rise  in  temperature. 
By  exactly  reversing  the  change,  the  quantity  of  heat 
which  had  disappeared  is  reproduced.  Latent  heat  is 
commonly  divided  into  latent  heat  of  fusion  and  latent 
heat  of  evaporation. 

Q.  What  is  latent  heat  of  fusion  ? 

The  act  of  liquefaction,  such  as  the  melting  of  ice,  con- 
sists of  interior  work — that  is,  of  work  expended  in  mov- 
ing the  atoms  into  new  positions.  If  a  piece  of  ice,  re- 


JOULE'S    EQUIVALENT. 


157 


duced  in  temperature  to,  say,  o°  F.,  is  subjected  to  the 
influence  of  heat,  its  temperature  will  rise  progressively 
for  each  increment  of  heat  received,  until  the  temperature 
of  the  ice  reaches  32°  F.,  when  the  melting  of  the  ice  will 
begin.  It  will  also  be  observed  that,  continuing  the  ap- 
plication of  the  heat  to  the  ice,  as  before,  there  is  no  cor- 
responding rise  in  temperature  either  in  the  ice  or  in  the 
water  in  contact  with  the  ice  so  long  as  any  of  the  latter 
remains  unmelted;  and  that  during  the  process  of  melting 
the  temperature  of  the  water  is  constant,  and  at  32°  F. 

This  change  of  state  from  solid  to  liquid,  in  the  melting 
of  one  pound  of  ice,  requires  143  units  of  heat,  the  tem- 
perature being  constant  at  32°  F.  The  heat  does  not 
raise  the  temperature  of  the  ice,  but  disappears  in  causing 
its  condition  to  change  from  the  solid  to  the  liquid  state. 
This  is  called  the  latent  heat  of  fusion. 

Q.  What  is  Joule's  equivalent? 

The  exact  mechanical  equivalent  of  heat  was  first  demon- 
strated experimentally  by  Dr.  Joule,  of  Manchester,  Eng- 


FlG.    13. 


land,  the  apparatus  employed  by  him  being  represented  in 
Fig.  13.     A  known  weight  was  connected  by  means  of 


158  COMBUSTION    OF    COAL. 

cords  to  a  shaft  /,  mounted  on  friction  wheels  not  shown 
in  the  illustration.  On  this  shaft  a  pulley  was  secured, 
which  through  the  medium  of  another  cord  imparted  motion 
to  the  shaft  r,  and  caused  it  to  revolve.  At  the  lower  end 
of  this  shaft  r  were  fitted  eight  sets  of  paddles,  which,  when 
connected  by  means  of  a  pin  P,  revolved  with  it.  To  the 
interior  of  the  copper  vessel  B  were  attached  four  station- 
ary vanes,  cut  out  in  such  manner  as  to  permit  the  free 
revolution  of  the  revolving  paddles.  Precautions  were 
taken  to  prevent  a  transfer  of  heat  from  the  vessel  B, 
which  need  not  be  described  here.  This  vessel  was  filled 
with  a  known  weight  of  water,  at  the  temperature  of  its 
greatest  density,  39°  F.,  and  a  thermometer  /  was  inserted 
in  the  vessel  B,  to  mark  the  rise  in  the  temperature  of  the 
water.  The  experiment  consisted  in  allowing  the  weight 
to  descend  by  its  own  gravity,  and,  through  the  medium  of 
the  cords,  to  cause  the  paddles  to  revolve  and  agitate  the 
water  in  the  vessel  B. 

After  many  hundreds  of  experiments  extending  through 
several  years,  Dr.  Joule  finally  fixed  upon  772  pounds, 
raised  one  foot  high  against  the  action  of  gravity,  as 
the  mechanical  equivalent  of  the  quantity  of  heat  neces- 
sary to  raise  the  temperature  of  one  pound  of  water 
through  i  °  F. ,  at  the  maximum  density  of  water,  39°  to 
40°  F. 

Q.  Is  the  relation  between  heat  and  mechanical  energy 
a  fixed  or  definite  one? 

Heat  and  mechanical  energy  are  mutually  convertible ; 
and  heat  requires  for  its  production,  and  produces  by  its 
disappearance,  mechanical  energy  in  the  proportion  of  772 
foot-pounds  for  each  British  unit  of  heat,  the  said  unit 
being  the  amount  of  heat  required  to  raise  the  tempera- 


SPECIFIC    HEAT.  159 

ture  of  one  pound  of  water  by  i°  F.,  near  the  temperature 
of  its  greatest  density,  39°  to  40°  F. 

Q.  What  is  specific  heat? 

The  specific  heat  of  a  substance  means  the  quantity  of 
heat  which  must  be  transferred  to  a  unit  of  weight  (such 
as  a  pound)  of  a  given  substance,  in  order  to  raise  its  tem- 
perature, by  one  degree,  as  compared  with  that  quantity 
of  heat  necessary  to  raise  an  equal  weight  of  water  through 
one  degree  at  its  greatest  density,  i.e.,  from  39°  to  40°  F. 
The  specific  heat  of  water  is  greater  than  that  of  any  other 
known  substance ;  it  thus  becomes  the  standard  for  com- 
parison. 

For  ordinary  calculations  we  may  assume :  Woods  aver- 
age one-half  the  specific  heat  of  water ;  coal  and  coke,  two- 
tenths  the  specific  heat  of  water ;  wood  charcoal,  one-fourth 
the  specific  heat  of  water. 

The  specific  heat  of  gases  varies  as  between  specific 
heat  under  constant  volume,  and  specific  heat  under  con- 
stant pressure.  Suppose  one  pound  of  gas  to  be  heated- — 
air,  for  example;  a  rise  in  temperature  occurs,  and  if  the 
air  is  free  to  expand  additional  heat  will  be  required  to 
perform  the  work  thus  done  by  expansion ;  but  if  the  air 
is  confined  so  that  no  expansion  can  occur,  less  heat  will 
be  required  to  raise  its  temperature  through  one  degree. 
The  specific  heat  of  air  for  equal  weights  (water  =  i)  at 
constant  pressure  is  0.2377,  at  constant  volume  it  is 
o.  1688,  the  difference  in  quantity  of  heat  is  0.2377  -f- 
0.1688  —  1.4081  times. 


CHAPTER  VII. 

FUEL   ANALYSIS. 

Q.  What  is  meant  by  the  elementary  analysis  of  coal  ? 

The  separation  of  coal  into  its  constituent  elements 
may  be  simply  to  know  what  elements  compose  it ;  such  a 
process  is  called  qualitative  analysis.  When  the  quantity 
of  each  element  is  to  be  determined,  it  is  then  known  as 
quantitative  analysis. 

The  elementary  analysis  of  coal  shows  it  to  be  princi- 
pally composed  of  the  following  simple  substances :  car- 
bon, hydrogen,  nitrogen,  oxygen,  sulphur,  ash.  Ash  is 
not  a  simple  substance,  but  represents  the  incombustible 
matter  of  whatever  composition  remaining  in  the  furnace 
after  combustion. 

The  elementary  analysis  of  coal  is  not  now  the  general 
practice ;  for  all  ordinary  purposes  the  shorter  method  of 
determining  the  moisture,  volatile  combustible  matter,  the 
fixed  carbon  and  ash  by  proximate  analysis  is  employed  in 
furnace  work. 

Q.  What  is  carbon  ? 

Carbon  is  one  of  the  most  widely  diffused  and  abundant 
of  the  elements.  It  occurs  in  nature  in  a  free  state  and 
in  combination  with  other  elements,  notably  in  the  form 
of  carbonates  and  as  an  essential  constituent  of  organic 
bodies. 

Carbon  in  its  free  state  is  a  solid,  infusible,  non-volatile 


CARBON. 


substance,  without  taste  or  smell,  exhibiting  great  diver- 
sity in  the  physical  characteristics  of  its  three  allotropic 
forms — diamond,  graphite,  and  charcoal.  It  is  the  princi- 
pal constituent  of  anthracite  coal.  It  constitutes  about 
one-half  of  bituminous  coal.  It  may  be  separated  from 
wood  in  the  form  of  charcoal  by  distilling  off  the  more 
volatile  elements. 

Carbon  unites  directly  with  oxygen,  sulphur,  nitrogen, 
and  a  few  of  the  metals,  the  latter  at  high  temperatures 
only.  The  two  direct  inorganic  compounds  of  carbon  and 
oxygen  are  known  as  carbonic  oxide,  CO,  and  carbonic  acid, 
CO2.  The  proportions  are  shown  in  the  following  table : 

TABLE  19. — ELEMENTARY  COMPOSITION  OF  CARBONIC  OXIDE  AND 
CARBONIC  ACID  GASES. 


COMPOSITION. 

By  weight. 

Percentage. 

Carbon. 

Oxygen. 

Total. 

Carbon. 

Oxygen. 

Total. 

Carbonic  oxide  CO. 
Carbonic  acid  CO3. 

12 
12 

16 
32 

28 
44 

42.86 
27.27 

57-14 

72-73 

TOO 

IOO 

These  are  the  two  principal  gases  formed  in  the  furnace 
by  the  combustion  of  the  carbonaceous  portions  of  the 
fuel. 

Carbon  and  hydrogen  unite  in  the  production  of  an  ex- 
tended series  of  hydrocarbons,  the  simpler  ones  being  the 
marsh  gas  series,  the  olefiant  gas  series,  and  the  benzole 
series.  When  carbon  and  hydrogen  are  further  combined 
with  the  addition  of  nitrogen  the  hydrocarbon  series  is 
greatly  extended,  including  aniline,  pyridine,  etc.,  all  of 
which  may  be  obtained  by  the  distillation  of  coal. 

Almost  all  the  elementary  substances  of  which  the  spe- 
ii 


1 62 


COMBUSTION    OF   COAL. 


cific  heat  and  atomic  weight  are  known,  give,  when  these 
two  properties  are  multiplied  into  each  other,  a  product 
averaging  not  far  from  6.34.  Carbon  is  one  of  the  excep- 
tions, as  shown  in  the  accompanying  table. 

Weber,  about  1872,  made  a  careful  series  of  determina- 
tions of  the  specific  heat  of  carbon,  the  results  of  which 
are  as  follows : 

TABLE  20. — SPECIFIC  HEAT  OF  CARBON. 


Temperature. 

Specific  heat. 

Specific  heat 
X  atomic  weight. 

Carb 
Car 

Pore 

>on  (diatr 
i 

on  (gra 
>us  wood 

iond)  

-    50°  C. 

+    10 
85 
250 
606 
985 
-    5o 

+     10 

61 

201 
250 
641 
978 

o°—  23°  C. 
o°—  99 
o°  —  223 

•  0635 
.1128 

.1765 
.3026 
.4408 

.4589 
.1138 
.1604 
.1990 
.2966 
.325 
•  4554 
•  457 
.1653 
.1935 
.2385 

0.76 

L35 

2.12 
3.63 
5.29 
5.51 

1.37 
1.93 
2.39 
3-56 
3.88 
5-35 
5.50 
1-95 
2.07 
2.84 

jhite)      

carbon  



These  numbers  show  that  the  specific  heat  of  carbon  in- 
creases as  the  temperature  increases,  and  that  the  value  of 
this  increase  for  a  given  temperature  is  considerably  less 
at  high  than  at  low  temperatures. 

Q.  What  is  meant  by  the  allotropic  states  of  carbon? 

The  term  allotropic  merely  expresses  the  several  condi- 
tions in  which  carbon  exists,  each  condition  having  widely 
different  physical  properties,  while  the  chemical  properties 
remain  the  same.  Carbon  occurs  as  diamond,  graphite, 
and  charcoal.  These  three  solids  are  wholly  unlike  in 


.DIAMOND.  163 

physical  properties,  yet  chemically  they  are  the  same— 
that  is,  they  yield  upon  analysis  nothing  but  pure  carbon. 
Investigations  by  Petersen,  undertaken  with  a  view  to 
determine,  if  possible,  the  relation  between  changes  of 
volume  and  of  energy  in  passing  from  one  allotropic  modi- 
fication of  an  element  to  another,  led  him  to  the  conclusion 
that  true  allotropic  varieties  differ  in  the  variety  of  energy 
they  contain,  in  specific  gravity,  in  specific  heat,  and  in 
solubility.  Color  and  crystalline  form  he  considers  of 
secondary  importance.  His  results  are  : 

Carbon-                                         oxida^on  (CO,).  At°miC  V°lume' 

Amorphous 9°5-3  to  969.8  6.  7  to  8.0 

Graphite 933-6  5.3 

Diamond 932. 4  to  945. 5  3.4 

Q.  What  are  the  physical  properties  of  the  diamond? 

The  diamond  is  a  natural  form  of  carbon,  crystallizing 
in  the  cubic  system.  It  was  shown  to  be  combustible  in 
1694,  and  Lavoisier  proved  that  the  sole  product  of  its 
combustion  was  carbonic-acid  gas,  CO2.  The  diamond  is 
noted  for  its  great  hardness.  Its  specific  gravity  ranges 
from  3.51  to  3.55,  averaging  about  3.51.  The  purest 
stones  are  practically  colorless.  The  index  of  refraction 
is  higher  in  the  diamond  than  in  any  other  known  trans- 
parent substance. 

On  exposure  to  the  heat  of  the  electric  arc  the  diamond 
swells  up,  cracks  on  the  surface,  and  becomes  coated  with 
a  substance  resembling  graphite.  The  study  of  the  action 
of  heat  upon  the  diamond,  with  and  without  the  presence 
of  air,  gave  the  earliest  clew  to  its  chemical  composition. 
On  the  combustion  of  the  diamond  there  remains  a  quan- 
tity of  a  colorless  or  reddish  ash,  varying  from  -^^  to  ^THTTT 
of  the  original  weight  of  the  mineral.  Microscopic  ex- 


164  COMBUSTION   OF.  COAL. 

amination  of  this  delicate  spongy  ash  has  led  investiga- 
tors to  the  belief  that  it  shows  traces  of  cellular  tissue, 
suggestive  of  a  vegetable  origin.  In  its  ordinary  state  the 
diamond  does  not  conduct  electricity,  but  the  cokelike 
mass  obtained  by  exposure  to  the  arc  is  a  good  conductor. 

Q.  What  are  the  physical  properties  of  graphite? 

Graphite  is  an  impure  variety  of  native  carbon,  known 
also  as  plumbago,  and  popularly  known  as  black  lead.  It 
occurs  usually  in  compact  and  crystalline  masses,  but  oc- 
casionally in  six-sided  tabular  crystals  which  cleave  into 
flexible  laminae  parallel  to  the  basal  plane.  Its  color  is 
iron  black  or  steel  gray,  with  metallic  lustre.  Its  specific 
gravity  is  1.9  to  2.6. 

Graphite  is  largely  used  in  the  manufacture  of  crucibles 
and  other  objects  required  to  withstand  high  temperatures. 
It  is  also  used  in  the  manufacture  of  lead  pencils,  as  a 
lubricating  agent,  as  a  stove  polish,  as  a  paint,  etc. 

Graphite  is  a  good  conductor  of  electricity,  and  is  much 
used  in  electrotyping,  the  moulds  upon  which  the  metal  is 
to  be  deposited  receiving  a  conducting  surface  by  being 
coated  with  finely  divided  graphite. 

Q.  What  are  the  physical  properties  of  charcoal? 

Charcoal  is  the  carbonaceous  residue  from  wood  or  other 
vegetable  matter,  partially  burnt  under  circumstances  which 
exclude  the  air,  and  from  which  all  watery  and  other  vola- 
tile matter  has  been  expelled  by  heat. 

The  composition  of  charcoal  depends  on  the  temperature 
at  which  it  is  produced.  At  high  temperatures  all  the 
oxygen  and  hydrogen  are  expelled  and  the  black  charcoal 
consists  of  carbon  and  the  mineral  matter  (ash)  originally 
present.  When  produced  at  lower  temperatures  the  char- 


CHARCOAL. 


I65 


ring  is  imperfect,  and  a  reddish  charcoal  results,  which 
contains  both  hydrogen  and  oxygen. 

Good  charcoal  is  black,  gives  a  sonorous  ring  when 
struck,  and  breaks  with  more  or  less  conchoidal  fracture 
and  a  ligneous  texture.  It  is  easily  pulverizable,  but  does 
not  crumble  under  moderate  pressure.  It  burns  without 
smoke  and  in  separate  pieces  without  flame.  The  specific 
gravity  of  wood  charcoal,  exclusive  of  pores,  is  1 . 5  to  2  ; 
inclusive  of  pores,  from  0.20  to  0.35  in  soft  charcoal,  and 
from  0.35  to  0.50  in  hard  charcoal. 

Q.  How  is  charcoal  affected  by  the  temperature  at  which 
it  is  made  ? 

The  composition  of  charcoal  produced  at  various  tem- 
peratures, as  determined  by  Violette — the  wood  experi- 
mented on  being  that  of  black  alder  or  alder  buckthorn, 
which  furnishes  a  charcoal  suitable  for  gunpowder — is 
given  in  the  annexed  table : 

TABLE  21. — COMPOSITION  OF  CHARCOAL.      (Violette.) 


Temperature 
of  carbonization. 

COMPOSITION  OF  THE  SOLID  PRODUCT. 

Carbon 
for  a  given 
weight 
of  wood. 
Per  cent. 

Carbon. 
Per  cent. 

Hydrogen. 
]  Per  cent. 

Oxygen, 
nitrogen 
and  loss. 
Per  cent. 

Ash. 
Per  cent. 

302°  F  .  . 

47.51 

51.82 

65.59 
73-24 
76.64 
81.64 
81.97 
83.29 
88.14 
90.81 
94-57 

6.12 

3.99 
4.8l 

4.25 
4.14 
4.96 
2.30 
1.70 
1.42 
1.58 
0.74 

46.29 
43.98 
28.97 
21.96 
18.44 
15.24 
14.15 
13-79 
9.26 

6.49 
3.84 

0.08 
0.23 
0.63 

o.57 
0.61 
.61 
.60 

.22 
.20 
.15 

0.66 

47-51 

39-88 
32.98 
24.61 
22.42 
15.40 
15-30 
15-32 
15.80 
15.85 
16.36 

OQ2 

482 

C72 

662 

810 

1873 

20  1  2 

2282 

2^72 

27^2 

The  products  obtained  at  the  first  two  temperatures,  viz., 
302°,  392°  F.,  cannot  be  properly  termed  charcoal. 


166  COMBUSTION    OF   COAL. 

Q.  How  is  the  combustibility  of  charcoal  affected  by  the 
temperature  at  which  it  is  made  ? 

Regarding  the  combustibility  of  charcoal,  that  made  at 
500°  F.  burns  most  easily;  and  that  made  between  1832° 
and  2732°  F.  cannot  be  ignited  like  ordinary  charcoal; 
that  made  at  a  constant  temperature  of  572°  F.  takes  fire 
in  the  air  when  heated  to  between  680°  and  715°  F.,  ac- 
cording to  the  nature  of  the  wood  from  which  it  has  been 
derived.  Charcoal  from  light  woods,  other  things  being 
equal,  ignites  most  easily.  Charcoal  produces  a  greater 
heat  than  an  equal  weight  of  wood. 

Charcoal,  not  being  decomposable  by  water  or  air,  will 
endure  for  any  length  of  time  without  alteration. 

Q.  What  elementary  substances  and  compounds  enter 
into  the  composition  of  charcoal? 

The  following  analysis  of  charcoal  shows  the  percent- 
ages of  elements  and  compounds  entering  into  its  com- 
position, instead  of  reducing  to  elements  alone : 

Carbon,  C 85.10  per  cent. 

Carbonic  acid  gas,  CO2 3. 26 

Carbonic  oxide,  CO i.  36 

Marsh  gas,  CH4 o.  70 

Hydrogen,  H 0.07 

Nitrogen,  N o.  51 

Water,  H2O 7-oo 

Ash  . .  2.00 


I  GO.  OO 


Q.  What  is  the  object  of  converting  wood  into  charcoal  ? 

The  carbonization  of  wood  is  intended  to  remove  those 
constituents  which  absorb  heat,  and  to  concentrate  the 
carbon,  which  possesses  great  heating  power.  The  sub- 
stances absorbing  heat  are  the  hygroscopic  water  and  oxy- 
gen contained  in  the  wood,  which,  on  combustion,  cause 


HEATING    POWER    OF   CARBON.  167 

the  formation  of  so  much  water  that  the  temperature  is 
decreased  to  a  considerable  degree.  Slow  charring  and 
low  heat  will  produce  the  largest  amount  of  charcoal,  but 
it  will  be  weak.  A  brisk  heat,  well  conducted,  will  fur- 
nish less,  but  will  make  a  strong  coal.  This  determines 
which  mode  of  charring  is  most  profitable  to  maker  and 
user.  With  a  well-conducted  operation  in  a  pit  contain- 
ing at  least  50  cords  of  wood  the  yield  for  air-dried  wood 
ought  to  be  in  the  proportion  here  shown : 

Kind  of  wood.                                                              Yield  by  weight.  Yield  by  measure. 

Oak 23  per  cent.  74  per  cent. 

Beech 22        "  73 

Pine 25        "  63 

A  cord  of  1 28  cubic  feet  of  oak  ought  to  furnish  64  bushels 
of  2,600  cubic  inches  each  ;  pine  wood  must  yield  54  bush- 
els. This  measure  is  actually  reached  by  good  burners, 
though  not  by  the  average  workman. 

Q.  Is  the  heating  power  of  carbon  affected  by  its  den- 
sity? 

Gruner  has  shown  that  the  less  the  density  of  any  form 
of  carbon,  the  greater  is  its  heating  power.  The  tests  he 
records  also  show  that  the  coals  containing  hydrogen  give 
a  greater  heating  power  than  that  calculated  by  theory 
from  their  elementary  composition.  It  would  naturally 
be  inferred,  therefore,  that  the  coals  which  have  the  least 
density,  and  which  contain  the  largest  percentage  of  dis- 
posable hydrogen,  would  have  the  greatest  heating  power. 
Yet  the  reverse  of  this  appears  to  be  true,  so  that  after 
the  disposable  hydrogen  reaches  four  per  cent  its  further 
increase  seems  to  be  actually  accompanied  by  a  decrease 
of  heating  power,  as  determined  by  a  calorimeter,  and  by 
a  still  greater  decrease,  as  shown  in  the  diminution  of 


l68  COMBUSTION    OF   COAT,. 

efficiency,  from  65  to  55  per  cent  in  the  industrial  or 
steaming  power.  It  is  difficult  to  explain  the  anomaly, 
except  upon  the  hypothesis  that  the  calori metric  determi- 
nations of  the  more  volatile  coals  were  inaccurate  (Kent). 

Q.  What  is  sulphur? 

Sulphur  is  often  found  in  coal  in  combination  with  iron, 
and  is  known  as  iron  pyrites.  Sulphur  is  highly  inflam- 
mable, and  when  heated  in  the  air  to  a  temperature  of 
about  482°  F.  it  takes  fire  and  burns  with  a  clear  blue, 
feebly  luminous  flame,  being  converted  into  sulphurous 
oxide,  SO2.  In  its  chemical  relations  sulphur  is  the  rep- 
resentative of  oxygen,  to  which  it  is  equivalent,  atom  to 
atom.  Oxygen  gas  and  sulphur  vapor  alike  support  the 
combustion  of  hydrogen,  charcoal,  phosphorus,  and  the 
metals  to  form  precisely  analogous  compounds.  The 
atomic  weight  of  sulphur  is  32;  symbol  S;  specific  heat, 
0.1776;  specific  gravity,  2.00. 

Q.  What  is  hydrogen  ? 

Hydrogen  is  found  free  in  nature  among  the  gases 
evolved  from  certain  volcanoes;  also  in  the  gases  given 
off  from  the  oil  wells  of  Pennsylvania.  It  is  one  of  the 
many  gases  of  which  coal  gas  is  a  mixture.  It  exists  in 
air  in  small  quantities,  in  combination  with  nitrogen  as 
ammonia. 

Hydrogen  when  pure  is  a  colorless,  invisible  gas,  with- 
out smell  or  taste.  It  is  the  lightest  body  known,  and 
has  a  specific  gravity  of  0.0693  (air  =  i.oooo).  It  is  but 
slightly  soluble  in  water.  The  specific  heat  of  hydrogen 
for  equal  weights  at  constant  pressure  =  3.4046;  for  con- 
stant volume  =  2.4096. 

Hydrogen  burns   in  the  air  with   an  almost  colorless 


HYDROGEN.  169 

flame,  but  under  certain  conditions,  even  when  pure,  the 
centre  of  the  flame  is  colored  green  while  the  external 
portions  are  of  a  violet  blue  color.  On  reducing  the  press- 
ure the  blue  color  is  transferred  to  green,  and  from  that 
successively  to  yellow,  orange,  and  red.  The  refrangibil- 
ity  of  the  emitted  light  becomes  less  when  the  intensity 
of  combustion  is  reduced  by  a  diminution  in  the  supply  of 
oxygen  or  by  a  reduction  of  pressure.  A  lighted  taper  is 
extinguished  on  being  placed  in  a  jar  of  hydrogen,  and  the 
gas  burns  at  the  mouth  of  the  jar,  rapidly  if  the  jar  be 
mouth  upward,  slowly  if  mouth  downward. 

When  mixed  with  air  or  oxygen,  hydrogen  burns  with 
explosive  rapidity.  The  loudest  explosion  is  obtained  by 
mixing  two  volumes  of  hydrogen  and  one  volume  of  oxy- 
gen. The  maximum  explosive  effect  with  air  is  obtained 
by  mixing  one  volume  of  hydrogen  with  two  and  a  half 
volumes  of  air,  but  the  explosion  in  this  case  is  not  so 
powerful  on  account  of  the  nitrogen  present.  In  each  of 
these  cases  the  two  gases  are  present  in  the  proportion  in 
which  they  unite  to  form  water.  This  mixture  of  hydro- 
gen and  oxygen  is  not  explosive  at  greatly  reduced  press- 
ure. A  rarefaction  produced  by  diminution  of  pressure  is 
more  effective  in  weakening  the  force  of  an  explosion  than 
diluting  the  mixture  with  an  indifferent  gas. 

Favre  and  Silbermann  ascertained  the  heat  of  one  pound 
of  hydrogen  burned  in  oxygen  to  be  sufficient  to  raise  the 
temperature  of  62,032  pounds  of  water  i°  F.  This  is  not 
equalled  by  any  other  known  substance. 

The  liquefaction  and  solidifying  of  hydrogen  was  ac- 
complished by  Pictet  in  1878.  The  melting  point  of 
hydrogen  ice  as  given  by  Dewar  is  16°  or  17°  absolute 
(—257°  or  —256°  C.).  Solid  hydrogen  seems  to  possess 
the  properties  of  the  non-metallic  elements  rather  than 


1 70  COMBUSTION   OF   COAL. 

that  of  the  metals,  among  which  it  has  been  usual  to  class 
hydrogen. 

Q.  What  is  carbureted  hydrogen? 

Carbureted  hydrogen  is  obtained  by  the  distillation  of 
the  volatile  portions  of  bituminous  coal.  It  has  long  been 
employed  as  an  illuminating  agent.  Coal  gas  will  vary 
according  to  the  coal  from  which  it  is  distilled,  but  the 
following  fairly  represents  the  average  composition  of  car- 
bureted hydrogen : 

Hydrogen 41-85 

Marsh  gas 39. 1 1 

Carbonic  oxide 5-86 

Olefines 7-95 

Nitrogen 5-Qi 

Carbonic  acid .22 


100.00 

Q.  What  is  marsh  gas? 

Marsh  gas  is  emitted  from  the  surface  of  the  ground  in 
many  parts  of  the  world,  notably  in  Italy,  North  America, 
and  in  the  vicinity  of  the  Caspian  Sea.  It  is  formed  by 
the  putrefaction  of  vegetable  matter  under  water,  and 
hence  occurs  in  marshy  places.  It  also  occurs  in  the  coal 
measures,  where  it  is  known  as  fire  damp,  being  produced 
by  the  destructive  distillation  of  carbonaceous  matter,  oc- 
curring to  the  extent  of  about  forty  per  cent  by  volume  in 
coal  gas. 

Marsh  gas  (methyl  hydride)  is  colorless  and  odorless, 
and  forms  an  explosive  mixture  with  air.  Its  specific 
gravity  is  0.5596  (air  =  i.oooo). 

The  marsh  gas  series  consists  of : 

Formula.  Specific  gravity. 

Methyl  hydride CH4  o.  5596 

Ethyl         '•        C2H6  1.037 

Propyl        "        C3H8  1.522 


OLEFIANT    GAS.  I /I 

Formula.     Specific  gravity. 

Butyl  hydride C4Hi()          2.005 

Amyl         "       C6H12          2.489 

Hexyl        "        C6H14          0.669 

Octyl         "        CsHiH          0.726 

Decyl        "       Ci  0H22 

Q.  What  is  olefiant  gas? 

This  gas  occurs  through  the  dry  distillation  of  many 
organic  bodies ;  hence  occurs  to  the  extent  of  four  to  five 
per  cent  in  coal  gas. 

It  is  a  colorless  gas,  and  liquefies  at  a  pressure  of  42^ 
atmospheres  at  — 1.1°  C.  It  forms  an  explosive  mixture 
with  oxygen. 

The  olefiant  gas  series  consists  of : 

Formula.     Specific  gravity. 

Methylene   CH2  0.484 

Ethylene  (olefiant  gas) C2H4  0.978 

Prophylene  (tritylene) •  C3H6  1.452 

Butylene C4H8  I-93& 

Amylene C5H10  2.419 

Caproylene  (hexylene) C6HJ2  2.970 

(Enanthylene C7Hi4  3-32Q 

As  a  product  of  the  dry  distillation  of  coal  it  is  largely 
used  because  it  is  an  abundant  illuminating  constituent  in 
coal  gas,  its  technical  name  being  ethylene,  C2H4.  Pure 
ethylene  burnt  at  the  rate  of  5  cubic  feet  per  hour  emits 
a  light  equal  to  68.5  standard  candles.  The  illuminating 
power  of  a  given  quantity  of  ethylene  is  increased  by 
moderate  admixture  with  hydrogen,  carbonic  oxide,  or 
marsh  gas,  although  the  actual  amount  of  light  given  per 
cubic  foot  of  the  mixture  is  less  than  that  given  by  pure 
ethylene.  The  intrinsic  illuminating  power  is  reduced  by 
admixture  with  nitrogen,  carbonic  acid  gas,  water  vapor, 
but  increased  by  oxygen. 


1/2  COMBUSTION   OF   COAL. 

Q.  What  quantity  of  moisture  or  water  is  present  in 
coal? 

All  coals  contain  a  certain  amount  of  water  in  their 
composition.  This  water  can  be  evaporated  by  the  appli- 
cation of  heat,  but  coals  thus  deprived  of  moisture  will 
regain  by  absorption  from  the  atmosphere  the  precise 
quantity  which  had  been  previously  expelled. 

The  quantity  of  moisture  in  coal  varies  with  the  density 
and  structure,  so  that  no  averages  can  be  given ;  for  ex- 
ample : 

Lignites  vary  from 5  to  30  per  cent. 

Bituminous  coals  from i  to  12        " 

Semi-bituminous  coals  from i  to    5        " 

Anthracite  coals  from i  to    2        " 

Q.  What  is  meant  by  hygroscopic  moisture  ? 

The  hygroscopic  moisture  in  fuel  is  that  quantity  which 
is  always  held  by  the  fuel  when  exposed  to  the  atmosphere. 
All  fuels  contain  a  certain  amount  of  moisture  in  their 
composition,  which  may  be  expressed  as  "  water  of  condi- 
tion. "  This  moisture  may  be  temporarily  expelled  by 
heat,  only  to  be  reabsorbed  from  the  atmosphere  in  the 
exact  amount  thus  driven  off.  The  quantity  of  hygro- 
scopic moisture  thus  held  by  any  fuel  is  dependent  upon 
its  structure  and  density ;  the  greater  the  density  the  less 
the  contained  moisture. 

Q.  What  is  the  method  employed  for  obtaining  the 
proximate  analysis  of  coal? 

In  order  to  estimate  the  value  of  a  fuel,  it  is  necessary 
to  determine  the  moisture,  volatile  matter,  fixed  carbon, 
and  sulphur.  Professor  Thorpe  states  that  in  the  metal- 
lurgical laboratory  of  the  Normal  School  of  Science  and 


PROXIMATE    ANALYSIS.  173 

Royal  School  of  Mines  these  assays  are  performed  in  the 
following  manner : 

1.  Hygroscopic  moisture.     In  a  water  bath  heat  for  an 
hour  20  grains  of    powdered  sample   placed  in  a  watch 
glass.      Weigh  repeatedly  until  the  result  is  constant. 

2.  Coke.     Heat   1,000  grains  of  finely  powdered  sample 
in    large  covered  earthen    crucible    in   furnace   until    no 
flame  is  evolved.      Weigh  when  cold,  or,  better,  heat  50 
grains  in  platinum  crucible  with  lid  on,  the  loss  of  weight 
giving  volatile  matter. 

3.  Ash.     Heat  20  grains  of  finely  powdered  sample  in 
platinum  capsule  until  no  trace  of  carbon  is  left. 

4.  Sulphur.     Deflagrate  in  platinum  crucible  20  grains 
of  powdered  sample  with   500  grains  of  a  mixture  of  salt 
and  nitre  (2  :  i),  dissolve  in  water,  dilute  to  one-half  pint, 
add  HC1  in  slight  excess,  heat  for  twenty  minutes,  filter, 
and    to   filtrate    add   BaCl2.      Allow  to   stand  for   twelve 
hours,  filter,  weigh  precipitate. 

Q.  Why  does  not  the  percentage  of  sulphur  in  coal  ap- 
pear in  statements  accompanying  proximate  analyses  ? 

Because  the  proximate  analysis  determines,  first,  the 
volatile  and  non-volatile  quantities ;  and,  second,  the  com- 
bustible and  non-combustible  quantities  of  the  coal. 

No  sulphur  is  driven  off  in  the  heating  of  the  coal  to 
expel  its  moisture. 

When  heating  the  coal  to  distil  off  its  volatile  combus- 
tible matter  some  of  the  sulphur  passes  off  with  the  hydro- 
carbon gases.  The  sulphur  is  burnt  to  sulphurous  acid, 
then  a  certain  portion  of  this  is  oxidized  to  sulphuric 
acid.  The  amount  so  oxidized  will  depend  upon  circum- 
stances. If  the  sulphurous  acid  is  kept  hot  in  the  presence 
of  moisture,  then  oxidation  goes  on  more  rapidly;  but  if 


174  COMBUSTION   OF   COAL. 

it  be  cooled  down  almost  immediately  after  it  is  formed, 
the  action  is  very  slow. 

Whatever  sulphur  is  not  thus  driven  off  remains  in  the 
fixed  carbon  and  burns  during  the  ordinary  progress  of  the 
fire,  a  portion  uniting  with  the  earthy  matters  in  the  ash, 
becoming  more  or  less  inert. 

Q.  What  is  natural  gas? 

Natural  gas  is  found  locally  in  Western  Pennsylvania, 
Northern  Ohio,  and  Central  Indiana  in  paying  quantities ; 
in  lesser  quantities  it  is  found  in  many  other  localities. 
The  composition  of  natural  gas  at  Findlay,  Ohio,  is : 

By  weight.  By  volume. 

Hydrogen o.  27  2. 18 

Marsh  gas 90. 38  92. 60 

Carbonic  oxide o.  86  o.  50 

Olefiant  gas 0.53  0.31 

Carbonic  acid o.  70  o.  26 

Nitrogen 6. 18  3. 61 

Oxygen .  . .  .  o.  66  o.  34 

Sulphydric  acid o.  42  o.  20 


100.00 


The  heat  units  in  one  pound  of  this  gas  =  21,520;  the 
evaporative  power  of  one  pound  of  this  gas  from  and  at 
212°  F.  =  22.27  pounds  of  water. 

Tests  of  natural  gas  for  steam-making  conducted  at 
Pittsburg,  Pa.,  show  that  one  pound  of  good  bituminous 
coal  equals  from  7^  to  12^  cubic  feet  of  natural  gas. 
Other  experiments  show  that  1,000  cubic  feet  of  natural 
gas  equal  from  80  to  133  pounds  of  bituminous  coal,  a 
variation  of  more  than  60  per  cent  between  the  two  ex- 
tremes. Quality  of  coal  and  manipulation  of  furnace  ac- 
counts for  much  of  this  difference. 

The  chemical  composition  of  natural  gas,  as  shown  by 
an  average  of  four  samples  from  Indiana  and  three  from 


NATURAL   GAS. 

Ohio,  by  Prof.  C.  C.  Howard,  for  the  eleventh  annual  re- 
port of  the  U.  S.  Geological  Survey,  is  as  follows : 

Marsh  gas,  CH4 93-36 

Nitrogen 3-  28 

Hydrogen i.  76 

Carbon  monoxide 53 

Oxygen 29 

Olefiant  gas 28 

Carbon  dioxide 25 

Hydrogen  sulphide 18 

Total 99.93 

The  heat-producing  value  of  natural  gas,  as  compared 
with  other  fuel  gases  per  1,000  cubic  feet  at  40°  F.  and 
at  atmospheric  pressure,  is  given  by  Hosea  Webster  ap- 
proximately as  follows : 

Natural  gas 1,103,300  heat  units. 

Coal  gas 735,000 

Water  gas 322,000 

Producer  gas  (heated) 156,000         " 

Assuming  the  generation  of  steam  at  212°  from  water 
at  60°,  the  comparative  value  of  natural  gas  per  1,000 
cubic  feet  at  atmospheric  pressure  is  approximately  as 
follows : 

1,000  cubic  feet  natural    gas  evaporate 900  pounds. 

1,000  "        coal  600       " 

1,000  "        water  250       " 

1,000  "        producer"  "          115       " 

Natural  gas  is  an  ideal  fuel  if  used  near  the  source  of 
supply,  as  no  labor  is  required  in  its  use  except  to  regu- 
late the  supply  in  the  furnace.  It  is  not  difficult  to  regu- 
late the  supply  of  air  to  insure  perfect  combustion.  There 
is  no  soot,  ashes,  or  other  debris. 

Q.  What  is  producer  gas? 

Producer  gas  is  a  general  name  which  covers  any  method 
of  generating  gas  from  a  fuel  by  a  process  resembling  dis- 


1/6  COMBUSTION   OF   COAL. 

dilation,  the  gases  generated  being  conducted  to  the  place 
where  the  heat  of  combustion  is  to  be  utilized,  then  mixed 
with  air,  ignited  and  consumed.  This  system  offers  a 
remedy  for  the  imperfections  of  the  ordinary  fire  and  of 
various  fuels.  There  is  no  cinder,  no  ashes,  so  that  the 
surface  of  the  bodies  receiving  the  heat  is  not  altered. 
The  heating  is  effected  by  radiation  as  well  as  by  conduc- 
tion, and  inferior  classes  of  fuel  may  be  used. 

A  higher  calorific  power  may  be  obtained  by  producer 
gas  or  gaseous  fuel,  generally  on  account  of  the  smaller 
quantity  of  air  required  for  combustion  and  the  conse- 
quently lessened  dilution  of  heat  by  inert  nitrogen  and 
carbonic  acid.  The  gas  from  producers  worked  by  inter- 
nal combustion  contains  25  to  45  per  cent  of  combustible 
ingredients,  and  has  a  calorific  intensity  of  2867°  to 

3992°  F. 

Water  gas  and  ordinary  illuminating  gas  contain  86  to 
97  per  cent  combustible  matter.  The  waste  gases  from 
furnaces  may  be  used  instead  of  producer  gas  when  very 
high  temperatures  are  not  required,  and  where  variations 
in  temperatures  are  permissible,  as  steam  boilers,  hot 
blast,  etc.  Blast  furnace  gases  rarely  contain  30  per  cent 
carbonic  oxide,  usually  from  25  to  29  (Thorpe). 

Q.  What  is  the  composition  of  water  gas? 

A  sample  of  water  gas  from  Lowe's  gas  producers,  after 
passing  through  purifier  at  Novelties  Exhibition,  Philadel- 
phia, 1885,  analyzed  as  follows: 

Carbonic  oxide,  CO 44-5  volume. 

Hydrogen,  H 50.9 

Oxygen,       O)    {  j  .7 

Nitrogen,     N  J  ai  '  (  2. 8 

Undetermined i .  i 


GASEOUS    FUELS. 


177 


One  cubic  foot  of  water  gas  of  the  above  composition  will 
develop  in  burning  327  heat  units,  including  the  latent 
heat  of  evaporation  of  the  superheated  steam  which  es- 
capes in  the  chimney. 

Q.  What  is  Siemen's  gas? 

Siemen's  gas  is  a  fuel  gas  generated  in  a  furnace  con- 
structed upon  principles  developed  by  and  named  after  its 
inventor. 

The  average  composition  of  Siemen's  gas,  made  at  the 
Midvale  Steel  Works,  Philadelphia,  Pa.,  is: 

Carbonic  acid  gas,  CO2 i.  5  volume. 

Carbonic  oxide,  CO 23.6 

I  lydrogen,  II 6.  o 

Marsh  gas,  CH 4 3.0        " 

Nitrogen,  N 65.9 

100.0 

Q.  What  are  the  calorific  values  of  the  ordinary  gase- 
ous fuels  ? 

The  comparative  heating  effects  of  the  ordinary  gaseous 
fuels  are  given  below,  together  with  hydrogen : 

TABLE  22. — HEATING  POWER  OF  GASEOUS  FUELS. 


' 

Heat  units 
yielded  by  i 
cubic  foot. 

Cubic  feet 
needed  to 
evaporate 
100  Ibs.  water 
at  212°  Fahr. 

Hydrogen    H 

18^  i 

2Q3 

W^ater  gas  (from  coke) 

ica   I 

ati 

Blast  furnace  gas 

51   8 

1,038 

Carbonic  oxide,  CO                 .                               .... 

178.  ^ 

313 

Marsh  gas,  CH4          

571  .0 

93.8 

12 


CHAPTER  VIII. 

HEATING   POWER   OF    FUEL. 

Q.  How  may  the  calorific  value  of  fuel  be  determined  ? 

It  may  be  closely  estimated  by  calculation  if  the  mois- 
ture, volatile  matter,  and  fixed  carbon  have  been  previously 
obtained  by  proximate  analysis,  or  it  may  be  determined 
directly  by  means  of  a  calorimeter.  The  total  amount  of 
heat  obtainable  on  combustion  of  various  fuels  has  been 
determined  by  Rumford,  Lavoisier,  Andrews,  Favre  and 
Silbermann,  and  others.  The  general  principle  of  their 
methods  consisted  in  the  use  of  an  apparatus  (calorimeter) 
in  which  the  entire  heat  of  combustion  was  absorbed  by  a 
known  weight  of  water,  the  increase  in  the  temperature  of 
the  latter  being  ascertained  by  the  indication  of  thermom- 
eters suspended  in  it. 

Q.  Knowing  the  calorific  value  of  each  of  the  con- 
stituents of  any  fuel,  may  not  the  total  calorific  power  of 
fuel  be  determined  by  calculation  ? 

The  calorific  power  of  a  fuel  may  be  calculated  from  the 
results  of  an  organic  analysis ;  but  in  any  such  calculation 
the  oxygen  must  be  considered  to  be  in  combination  with 
sufficient  hydrogen  to  form  water,  H2O.  It  is  thus  only 
the  excess  of  carbon  and  hydrogen  (disposable  hydrogen) 
after  this  deduction  that  is  available  for  the  generation  of 
heat.  Such  calculations  have  been  found  only  to  approxi- 
mate to  the  truth,  coals,  excluding  lignite,  giving  a 


MOISTURE    IN    COAL.  1 79 

higher  calorific  power  with  the  calorimeter  than  that  ob- 
tained by  calculation. 

Q.  What  is  the  effect  of  moisture  in  coal  ? 

Whatever  moisture  or  water  is  contained  in  coal  must 
of  necessity  be  evaporated  in  the  fire  before  any  useful 
effect  is  obtained.  Inasmuch  as  some  of  the  poorer  varie- 
ties of  coal  contain  ten  or  even  fifteen  per  cent  of  water, 
this  evaporation  is  carried  on  at  considerable  loss  in  the 
furnace. 

Q.  How  may  the  loss  by  evaporation  of  moisture  in 
coal  be  estimated  ? 

Suppose  a  furnace  requires  10,000  pounds  of  coal  per 
day,  the  coal  containing  12  per  cent  moisture,  we  have: 

10,000  x  •  12  =  i, 200  pounds  of  water  to  be  evaporated. 
If  the  coal  is  60°  F.  it  must  be  raised  to  212°,  and  the 
contained  water  then  converted  into  steam  at  212°,  after 
which  it  abstracts  heat  from  the  furnace  until  the  steam 
and  gases  are  of  the  same  temperature,  say  2,000°  F. ;  we 
have  then : 

212° —  60° =         152°  difference  in  temp. 

Heat  units  per  pound  of  water  re- 
quired to  effect  the  conversion 
of  water  at  212°  into  steam  at 
212° =  966 


Total i ,  1 1 8  heat  units  per  pound  of 

water,  or,  for  1,200  pounds  of 

water  =  1,118  X  1,200 =  1,341,600 

Heat  units  to  be  supplied  1,200 
pounds  of  steam  at  212°  to  raise 

it   tO  2,000°=  2,000°  —  212°  X 

1,200 =2,  145,600 


Total 3,487, 200  heat  units,  representing 

lost  work  in  the  furnace. 


180  COMBUSTION    OF   COAL. 

Q.  How  should  the  evaporation  of  the  contained  water 
in  coal  be  credited  with  reference  to  the  furnace  ? 

Nothing  should  be  credited  the  furnace  but  heat  avail- 
able for  useful  work.  The  evaporation  of  water  from 
coal  in  the  furnace  is  not,  in  steam-making,  useful  work. 
It  counts,  therefore,  against  the  coal,  but  not  against  the 
possible  efficiency  of  the  boiler,  for  the  reason  that  if  a 
drier  and  better  quality  of  coal  were  burnt,  higher  evapo- 
rative results  would  naturally  follow.  Coals  heavily 
charged  with  moisture  are  used  only  because  drier  coals 
are  not  usually  available  at  a  price  which  would  reduce  the 
cost  of  steam-making. 

Q.  How  is  the  calorific  power  of  fuel  expressed? 

In  expressing  the  calorific  power  of  fuel,  the  amount  of 
heat  generated  by  the  combustion  of  carbon  to  carbonic 
acid  gas,  CO2,  is  taken  as  the  standard  of  comparison. 
Experimental  results  vary  only  in  slight  degree,  so  that  it 
is  generally  agreed  that  14,500  heat  units  are  evolved  by 
the  complete  combustion  of  one  pound  of  carbon  in  oxygen 
to  CO2.  As  the  unit  of  heat  varies  with  the  thermometric 
scale  and  the  unit  of  weight  employed,  it  will  be  understood 
that  the  above  refers  to  the  British  thermal  unit,  or  that 
amount  of  heat  required  to  raise  one  pound  of  water 
through  i°  F.  (39°  to  40°). 

Q.  Whaj:  is  the  unit  of  horse  power  for  steam  boilers  ? 

The  standard  unit  of  horse  power  is  the  equivalent  of 
33,000  pounds  raised  one  foot  high  in  one  minute.  It  is 
apparent  that  no  such  standard  can  be  applied  to  steam 
boilers.  The  evaporation  of  30  pounds  of  water  from  a 
temp'erature  of  100°  F.  into  steam  of  70  pounds  pressure 
above  the  atmosphere  was  the  standard  adopted  for  steam 


EVAPORATIVE    POWER    OF   COAL.  l8l 

boilers  by  the  Centennial  Committee,  on  the  belief  that 
30  pounds  of  water  evaporated  per  hour  represented  the 
average  requirement  of  steam  engines  per  indicated  horse 
power  (1876).  This  is  nearly  equivalent  to  34^2  pounds 
of  water  evaporated  from  and  at  212°  F.,  this  latter  re- 
quiring 33,305  heat  units. 

Q.  Is  there  any  fixed  relation  between  the  quantity  of 
fuel  burnt  in  a  boiler  furnace  and  the  unit  of  horse 
power  ? 

The  quantity  of  fuel  required  to  evaporate  the  water  in 
a  boiler  into  steam  has  nothing  whatever  to  do  with  the 
horse-power  unit.  But  if  we  may  assume  as  fair  average 
practice  an  evaporation  of  8  pounds  of  water  per  pound  of 
fuel,  and  a  consumption  of  3.75  pounds  of  fuel  per  horse 
power,  we  reach  the  figure  of  30  pounds  of  steam  per 
horse  power  per  hour.  For  a  horizontal  tubular  boiler  set 
in  brick  work,  1 5  square  feet  of  heating  surface  per  horse 
power  is  a  common  allowance,  and  will  develop  a  horse 
power  of  steam  under  all  ordinary  conditions,  the  ratio  of 
grate  surface  to  heating  surface  being  commonly  30  to  I. 

Q.  What  is  meant  by  the  evaporative  power  of  coal  ? 

By  evaporative  power  of  coal  is  meant  the  number  of 
pounds  of  water,  which,  under  certain  conditions,  are  capa- 
ble of  being  evaporated  per  pound  of  coal.  In  making  a 
complete  evaporative  test  it  is  necessary  to  know  the  tem- 
perature of  the  feed  water,  the  pressure  and  temperature 
of  the  steam,  the  number  of  pounds  of  coal  burnt  on  the 
grate,  and  the  number  of  pounds  of  water  evaporated  in  a 
given  time.  The  simple  evaporation  is  determined  by 
dividing  the  number  of  pounds  of  water  evaporated  in  a 
given  time,  say  ten  hours,  by  the  number  of  pounds  of 
coal  actually  burnt  during  the  same  time;  but  when  the 


1 82  COMBUSTION    OF   COAL. 

temperatures  of  the  feed  water  and  of  the  steam  are  to  be 
taken  into  account,  it  is  then  commonly  referred  to  as 
evaporation  from  and  at  212°. 

Q.  What  quantity  of  heat  is  absorbed  by  the  internal  work 
done  in  liberating  the  volatile  combustible  from  coal  ? 

The  investigations  of  E.  T.  Cox,  formerly  State  geolo- 
gist, Indiana,  upon  the  coals  of  that  State,  showed  that  the 
average  thermal  value  of  the  volatile  combustible  matter 
liberated  from  bituminous  coal  by  heat  during  its  combus- 
tion was  20, 1 1 5  heat  units,  and  that  to  liberate  one  pound 
of  these  gases  3,600  heat,  units  were  expended  in  over- 
coming the  internal  resistances  in  the  coal.  This  latter 
amount,  3,600  heat  units,  should  therefore  be  deducted 
from  the  total  heat  evolved  in  any  calculations  based  upon 
proximate  analyses,  to  get  accurate  thermal  values. 

The  calorific  value  of  coal  calculated  in  accordance  with 
the  above  paragraph  would  be  as  follows : 

A  sample  of  Indiana  bituminous  coal  yielded  by  proxi- 
mate analysis — 

Fixed  carbon 49.  51  per  cent. 

Volatile  combustible 37. 64       " 

Moisture 4. 30 

Ash 8.55 

100.00 

The  theoretical  calorific  value  with  Professor  Cox's  de- 
duction would  be  calculated  thus — 

British 
thermal  units. 

Volatile  combustible 3764  X  20,115  =  7.571-29 

Less 3764  X    3,6oo  =  1,355.04 

Net  value  of  volatile  combustible 6,216. 25 

Carbon 4951  X  14,544  =  7,200.73 

Total  calorific  value 13,416.98 


HEATING   VALUE    OF   COAL. 


I83 


Q.  Knowing  the  quantity  of  fixed  carbon  in  any  coal, 
may  the  approximate  heating  value  of  such  a  coal  be 
determined  by  calculation  ? 

Having  the  ultimate  analysis  of  a  coal,  Kent  states  that 
by  the  use  of  Dulong's  law,  it  can  be  predicted  what  that 
coal  will  give  in  the  calorimeter  within  three  per  cent. 
Having  only  the  proximate  analysis  one  can  predict  even 
from  that  very  closely  what  the  heating  value  of  the  coal 
is.  Dulong's  formula,  as  modified  by  Mahler,  is— 


in  which  O  is  quantity  of  heat  in  Centigrade  units,  and 
H,  O,  and  N  the  percentages  of  hydrogen,  oxygen,  and 
nitrogen. 

Mahler's  results  indicate  a  law  of  relation  between  the 
composition  of  the  coal  as  determined  by  proximate  analy- 
sis and  the  heating  value.  The  percentage  of  fixed  carbon 
in  the  dry  coal,  free  from  ash,  may,  in  the  case  of  all  coals 
containing  over  58  percent  of  fixed  carbon,  have  the  heat- 
ing power  predicted  with  a  limit  of  error  of  3  per  cent. 

TABLE   23.  —  APPROXIMATE   HEATING   VALUE   OF    COALS    BASED   UPON 
MAHLER'S  TESTS. 


Carbon,  per 

HEATINC 

,  VALUE. 

Carbon,  per 

HEATINC 

,  VALUE. 

cent,  dry  and 
free  from  ash. 

Calories. 

British 
thermal  units. 

cent,  dry  and 
free  from  ash. 

Calories. 

British 
thermal  units. 

Q7 

8,2OO 

14,760 

63  

8,400 

I5,I2O 

04             .... 

8,400 

I5,I2O 

60  

8,100 

14,580 

QO 

8  600 

15  480 

57  

7,8OO 

14,040 

87 

8  700 

15,660 

54  

7,4OO 

13,320 

80. 

8  800 

1  5  ,  840 

51  

7,OOO 

I2,6OO 

72 

8  700 

1  5  660 

CQ 

6  800 

12  240 

68 

8,600 

15,840 

Q.  What  is  Mahler >s  formula  ? 

Mahler's  formula  for  expressing  the  calorific  power  of 


184  COMBUSTION    OF    COAL. 

coal  and  hydrocarbon  fuels  is  a  modification  of  Dulong's 
formula,  and  is  thus  given  by  William  Kent : 
Mahler's  formula — 

()  _  8.140  C  +  34.  SOP  H-3.000  (O  +'N) 
100 

The  maximum  difference  between  Dulong's  formula  and 
the  actual  result  in  any  single  case  is  a  little  over  three 
per  cent ;  and  between  Mahler's  formula  and  the  actual, 
four  per  cent. 

Dulong's  formula,  Q  —  y^  [8,080  +  34>5°°  (H  —"•£)], 
has  the  advantage  of  being  more  strictly  a  theoretical  for- 
mula, based  merely  upon  the  observed  heating  power  of  the 
two  elements,  carbon  and  hydrogen,  and  the  assumption 
that  the  oxygen  renders  unavailable  for  heating  power  l/% 
of  its  weight  of  hydrogen,  while  Mahler's  formula  intro- 
duces a  coefficient,  3,000,  which  is  entirely  empirical,  and 
only  on  his  own  observations. 

The  figures  given  in  the  above  formula  are  French  and 
not  British  thermal  units. 

Q.  What  is  Dulong's  formula  ? 

Dulong  proposed  the  following  formula  as  expressive  of 
the  calorific  power  of  the  elements  carbon  and  hydrogen 
when  burnt  to  carbonic  acid  gas,  CO2,  and  steam,  H2O : 

Dulong's  formula— P  =  8,080  C  +  34,462  (H  —  f ), 
when  P  =  heating  power;  C  =  weight  of  carbon;  O  = 
weight  of  oxygen;  H  =  free  hydrogen,  i.e.,  total  hydrogen 
less  that  already  burnt  to  water  by  the  oxygen  which  the 
based  coal  contains. 

The  figures  in  the  above  formula  are  French  and  not 
British  thermal  units. 

It  is  now  established  by  the  labors  of  Favre,  Silbermann, 
Regnault,  Bertholet,  and  others,  that  the  heat  of  combus- 


THOMPSON'S  CALORIMETER. 


185 


tion,   like  specific  heat,  varies  with  the  density;  for  ex- 
ample : 

Calories. 


Carbon  from  charcoal  develops 8,080 

Carbon  of  gas  retorts,  more  dense 8,047 

Natural  graphite 7,  797 

Diamond 7,  770 


British 
thermal  units. 

15,544 
14,484 

14,034 
13,986 


Q.  What  are  the  details  of  construction  of  the  Thomp- 
son calorimeter  ? 

Referring  to  Fig.  14,  the  Thompson  calorimeter  consists 
of  a  glass  cylinder  A  closed  at  the 
lower  end  only,  to  contain  a  given 
weight  of  water.  B  is  a  cylindrical 
copper  vessel  called  the  condenser, 
closed  at  one  end  with  a  copper  cover, 
in  which  is  fixed  a  metal  tube  C,  com- 
municating with  the  interior  of  the  ves- 
sel B,  and  fitted  at  its  upper  extremity 
with  a  stopcock.  The  other  end  of  B 
is  open,  and  it  is  perforated  near  the 
open  end  by  a  series  of  holes,  b,  b.  D  is 
a  metal  base  upon  which  B  is  fixed  by 
means  of  three  springs,  which  are  at- 
tached to  D,  and  press  against  the  in- 
ternal surface  of  B,  but  which  are  omit- 
ted from  the  engraving.  A  series  of 
holes  is  arranged  round  the  circumfer- 
ence of  D  to  facilitate  raising  the 
apparatus  through  the  water.  E  is  a 
copper  cylinder,  called  the  furnace, 
closed  at  the  lower  end  only,  which 
fits  into  a  metal  ring  or  seat  on  the 
centre  of  D. 


FIG.  14. 


1 86  COMBUSTION   OF   COAL. 

Q.  In  what  manner  are  the  results  obtained  in  the 
Thompson  calorimeter  ? 

A  known  weight  of  fuel  is  burnt  by  means  of  chlorate 
of  potash  and  nitre  at  the  bottom  of  a  vessel  containing  a 
known  weight  of  water.  The  heat  produced  by  the  com- 
bustion of  the  fuel  is  communicated  to  the  water,  and 
from  the  rise  in  temperature  of  the  latter  is  calculated  the 
number  of  parts  of  water  which  the  combustion  of  one 
part  of  the  fuel  will  raise  one  degree  in  temperature. 
This  number  being  divided  by  the  latent  heat  of  steam, 
967  heat  units,  gives  the  evaporative  power  of  the  fuel, 
which  one  pound  of  the  fuel  is  theoretically  capable  of 
evaporating. 

In  the  instrument  described,  it  is  intended  that  30 
grains  of  the  fuel  should  be  burnt,  and  that  29,010  grains, 
or  967  times  this  weight,  of  water  should  be  employed. 
Hence  the  rise  in  the  temperature  of  the  water  expressed 
in  degrees  Fahrenheit  is  equal  to  the  number  of  pounds  of 
water  which  one  pound  of  the  fuel  theoretically  will  evap- 
orate ;  but  ten  per  cent  is  directed  to  be  added  to  this  num- 
ber as  a  correction  for  the  quantity  of  heat  absorbed  by  the 
apparatus  itself,  and  consequently  not  expended  in  raising 
the  temperature  of  the  water. 

Q.  In  what  manner  are  experiments  conducted  with  the 
Thompson  calorimeter  ? 

Thirty  grains  of  finely  powdered  fuel  is  intimately  mixed 
with  from  ten  to  twelve  times  its  weight  of  a  perfectly  dry 
mixture  of:  Chlorate  of  potash,  3  parts;  nitre,  I  part. 
The  resulting  mixture,  which,  for  the  sake  of  distinction, 
may  be  called  the  fuel  mixture,  is  introduced  into  the  fur- 
nace E,  and  carefully  pressed  or  shaken  down.  The  end 
of  a  slow  fuse,  about  half  an  inch  long,  is  next  inserted  in 


BARRUS'    CALORIMETER.  l8/ 

a  small  hole  made  in  the  top  of  the  fuel  mixture,  and  is 
fixed  there  by  pressing  the  latter  around  it.  The  furnace 
is  then  placed  in  its  seat  on  the  metal  base  D,  and  the 
fuse  lighted,  and  the  condenser  B  with  its  stopcock  shut 
fixed  over  the  furnace. 

The  cylinder  A  is  previously  charged  with  29,010  grains 
of  water,  the  temperature  of  which  must  be  recorded,  and 
the  apparatus  is  now  quickly  submerged  in  it.  The  fuse 
ignites  the  fuel  mixture,  and  when  the  combustion  is  fin- 
ished (indicated  by  the  cessation  of  the  bubbles  of  gas, 
produced  by  the  combustion,  which  rise  through  the  water), 
the  stopcock  is  opened,  and  the  water  enters  the  condenser 
by  the  holes  b,  b.  By  moving  the  condenser  up  and  down, 
the  water  is  thoroughly  mixed  and  acquires  a  uniform  tem- 
perature, which  is  then  recorded.  By  adding  ten  per  cent 
to  the  number  of  degrees  Fahrenheit  which  the  water  has 
risen  in  temperature,  the  theoretical  evaporative  power  of 
the  coal  is  at  once  approximately  determined. 

The  furnace  shown  in  Fig.  14  is  intended  to  be  used 
when  bituminous  coals  are  to  be  operated  upon ;  but  in 
experimenting  on  coke,  anthracite,  and  other  difficult  com- 
bustible fuels,  a  wider  and  shorter  furnace  is  preferred, 
and  the  fuel  mixture  should  not  be  pressed  down. 

Q.  What  is  the  construction  of  the  Barms'  coal  calorim- 
eter? 

The  Barrus'  coal  calorimeter,  shown  in  Fig.  15,  consists 
of  a  glass  beaker,  5  inches  in  diameter  and  10  inches  high, 
which  can  be  obtained  of  most  dealers  in  chemical  appa- 
ratus. The  combustion  chamber  is  of  special  form,  and 
consists  of  a  glass  bell  having  a  notched  rib  around  the 
lower  edge,  and  a  bead  just  above  the  top,  with  a  tube  pro- 
jecting a  considerable  distance  above  the  upper  end.  The 


188 


COMBUSTION   OF   COAL. 


bell  is  2^  inches  inside  diameter,  5^  inches  high,  and  the 
tube  above  is  ^  inch  inside  diameter,  and  extends  be- 
yond the  bell  a  distance  of  9  inches.  The  base  consists 
of  a  circular  plate  of  brass,  4  inches  in  diameter,  with 

three  clips  fastened  on  the  up- 
per side  for  holding  down  the 
combustion  chamber.  The  base 
is  perforated,  and  the  under  side 
has  three  pieces  of  cork  at- 
tached, which  serve  as  feet.  To 
the  centre  of  the  upper  side  of 
the  plate  is  attached  a  cup  for 
holding  the  platinum  crucible, 
in  which  the  coal  is  burned.  To 
the  upper  end  of  the  bell  be- 
neath the  bead,  a  hood  is  at- 
tached, made  of  wire  gauze, 
which  serves  to  intercept  the 
rising  bubbles  of  gas  and  retard 
their  escape  from  the  water. 
The  top  of  the  tube  is  fitted 
with  a  cork,  and  through  this  is 
inserted  a  small  glass  tube  which 
carries  the  oxygen  to  the  lower 
part  of  the  combustion  chamber. 
The  tube  is  movable  up  and 
down,  and  to  some  extent  sideways,  so  as  to  direct  the 
current  of  oxygen  to  any  part  of  the  crucible,  and  adjust 
it  to  a  proper  distance  from  the  burning  coal. 

In  addition  to  the  apparatus  here  shown  there  is  required 
a  tank  of  oxygen,  such  as  the  calcium  light  companies 
furnish,  scales  for  weighing  water,  and  delicate  balances 
for  weighing  coal,  besides  a  delicate  thermometer  for  tak- 


FIG.  15. 


BARRUS'    CALORIMETER.  189 

ing  the  temperature  of  the  water,  and  another  for  show- 
ing the  temperature  of  the  atmosphere.  The  former 
should  be  graduated  to  tenths  of  a  degree  Fahrenheit. 

The  quantity  of  coal  used  for  a  test  is  one  gram,  and  of 
water  2,000  grams.  The  equivalent  calorific  value  of  the 
material  of  the  instrument  is  185  milligrams.  One  degree 
rise  of  temperature  of  the  water  corresponds  to  a  total 
heat  of  combustion  of  2,185  British  thermal  units.  The 
number  of  degrees  rise  of  temperature  for  ordinary  coals 
varies  from  5^  to  6^°  F.  Radiation  is  allowed  for  by 
commencing  the  test  with  a  temperature  as  many  degrees 
below  the  atmosphere  as  the  temperature  rises  above  the 
atmosphere  at  the  end  of  the  test.  When  very  smoky 
coals  are  used,  the  sample  is  mixed  with  a  small  propor- 
tion of  anthracite  of  known  calorific  value ;  and  when  an- 
thracite coal  is  used,  a  small  percentage  of  bituminous  coal 
is  likewise  mixed  with  it. 

Q.  What  is  the  process  of  making  a  test  with  the 
Barrus'  calorimeter  ? 

Having  dried  and  pulverized  the  coal,  and  weighed  out 
the  desired  quantities  of  coal  and  water,  the  combustion 
chamber  is  immersed  in  the  water  for  a  short  time,  so  as 
to  make  the  temperature  of  the  whole  instrument  uniform 
with  that  of  the  water.  On  its  removal,  the  initial  tem- 
perature of  the  water  is  observed,  the  top  of  the  chamber 
lifted,  the  gas  turned  on,  and  the  coal  quickly  lighted,  a 
small  paper  fuse  having  previously  been  inserted  in  the 
crucible  for  this  purpose.  The  top  of  the  combustion 
chamber  is  quickly  replaced,  and  the  whole  returned  to  its 
submerged  position  in  the  water.  The  combustion  is  care- 
fully watched  as  the  process  goes  on,  and  the  current  of 
oxygen  is  directed  in  such  a  way  as  to  secure  the  desired 


190 


COMBUSTION    OF   COAL 


rate  and  conditions  for  satisfactory  combustion.  When 
the  coal  is  entirely  consumed,  the  interior  chamber  is 
moved  up  and  down  in  the  water  until  the  temperature  of 
the  whole  has  become  uniform,  and  finally  it  is  withdrawn 
and  the  crucible  removed.  The  final  temperature  of  the 
water  is  then  observed,  and  the  weight  of  the  resulting  ash. 
The  initial  temperature  of  the  water  is  so  fixed  by  suit- 
ably mixing  warm  and  cold  water  that  it  stands  at  the 
same  number  of  degrees  below  the  temperature  of  the  sur- 
rounding atmosphere  (or  approximately  the  same),  as  it  is 
raised  at  the  end  of  the  process  above  the  temperature  of 
the  air.  In  this  way  the  effect  of  radiation  from  the  ap- 
paratus is  overcome,  so  that  no  provision  in  the  matter  of 
insulation  is  required,  and  no  allowance  needs  to  be  made 
for  its  effect. 

Q.  What  are  some  of  the  results   obtained   by   the   use 
of  the  Barrus'  calorimeter  ? 

A  few  results  of  tests  with  the  Barrus'  coal  calorimeter 

are  here  given : 

TABLE  24. 


Kind  of  coal. 

Per  cent  of 
ash. 

TOTAL  HEAT  OF  COMBUSTION 
PER  POUND  OF  — 

Coal. 

Combustible. 

Georges  Creek,  bituminous.  .  .  . 

5-0 

6.5 
7.0 
8.6 
3.2 
4.0 
5-0 
6.5 
I.O 
3-5 
5-0 
5-9 

IO.2 

17-7 

13,487 
12,921 
13,360 
12,874 
14,603 
14,121 
14,114 
13,697 
14,455 
13,922 
13,858 
12,941 
11,664 
10,506 

14,196 
13,819 
14,365 
14,085 
15,085 
14,709 
14,856 
14,649 
I4,6OI 
14,426 
14,857 
13,752 
12,988 
12,765 

ti 

Pocahontas,  bituminous  

«                               .                      4< 

ci                    « 

New  River,  bituminous  
«                    11 

Youghiogheny,  bituminous  lump 
slack 

Frontenac,  Kansas,  bituminous. 

CARPENTER'S  CALORIMETER. 


191 


Q.  What  are  the  details  of  construc- 
tion of  the  Carpenter  calorimeter  ? 

Referring  to   Fig.   16,  the  appa- 
ratus   consists    of    the    combustion 
chamber  15,  which  has  a  removable 
bottom.     The  chamber  is  supplied 
with  oxygen  for  combustion  through 
tube  23,  the  products  of  combustion 
being  conducted  through  spiral  tube 
28,  29,  31.      The   tube    ends    in    a 
hose  nipple  30,  from  which  a  hose 
connection  is  made  to  a  small  cham- 
ber 39,  attached 
to  the  outer  case 
and      provided 
with    a     siphon 
gauge  40.     A 
plug,    41,    with 
pinhole,    is    at- 
tached   to  the 
chamber  for  the 
discharge    of 
gases.     The  si- 
phon gauge  indi- 
cates the  press- 
ure of  the  gases. 
Surrounding 
the    combustion 
chamber   is  a 
larger     closed 
chamber  i ,  filled 

FIG.  16. 

with   water  and 

connected  with  an  open  glass  tube  tfith  attached  scale  9 


IQ2  COMBUSTION   OF   COAL. 

and  10.  Above  the  water  chamber  is  a  diaphragm  12, 
which  is  used  to  adjust  the  zero  level  by  means  of  screw 
14  in  the  open  glass  tube  at  any  desired  point. 

A  glass  for  observing  the  process  of  combustion  is  in- 
serted at  33  in  top  of  the  combustion  chamber,  at  34  in 
top  of  water  chamber,  and  at  36  in  top  of  outer  case.  An 
opening  for  filling  is  provided  by  removing  the  plug  screw 
at  37,  which  can  also  be  used  for  emptying  if  desired. 
The  plug  17,  which  stops  up  the  bottom  of  the  combus- 
tion chamber,  carries  a  dish  22,  in  which  the  fuel  for  com- 
bustion is  placed,  also  two  wires  26,  27,  passing  through 
tubes  of  vulcanized  fibre,  which  are  adjustable  in  a  verti- 
cal direction  and  connected  with  a  thin  platinum  wire  at 
the  ends.  These  wires  are  connected  to  an  electric  cur- 
rent and  used  for.  firing  the  fuel.  On  the  top  part  of  this 
plug  is  placed  a  silver  mirror  38,  to  deflect  any  radiant 
heat.  Through  the  centre  of  this  plug  passes  a  tube  23, 
through  which  oxygen  passes  to  supply  combustion.  The 
plug  is  made  of  alternate  layers  of  rubber  and  asbestos 
fibre,  the  outside  only  being  of  metal,  which  being  in  con- 
tact with  the  wall  of  the  water  chamber  can  transfer  little 
or  no  heat  to  the  outside.  The  instrument  readily  slips 
into  an  outer  case,  which  is  nickel-plated  and  polished  on 
the  inside  so  as  to  reduce  radiation.  It  is  supported  on 
strips  of  felting,  5  and  6.  The  combustion  chamber  can 
be  subjected  to  considerable  pressure;  however,  10  inches 
water  pressure  has  usually  been  found  sufficient.  The  ca- 
pacity of  the  instrument  is  about  5  pounds  of  water,  and 
is  large  enough  for  the  combustion  of  2  grams  of  coal. 

Q.  What  advantages  are  possessed  by  the  Carpenter 
calorimeter  ? 

The  calorimeter  designed  by  R.  C.  Carpenter  differs 
from  other  calorimeters  by  the  provision  made  in  the  appa- 


COPPER-BALL   CALORIMETER.  IQ3 

ratus  itself,  for  giving  the  calorific  power  of  fuels  almost 
direct  in  British  thermal  units,  dispensing  also  with  some 
of  the  objectionable  features,  such  as  the  errors  involved 
in  the  thermometer,  the  determination  of  the  water  equiv- 
alent of  the  calorimeter,  correction  for  evaporation,  radia- 
tion, and  specific  heats,  thus  enabling  the  operator  to  do 
his  work  quickly  and  accurately.  This  apparatus,  shown 
in  Fig.  1 6,  is  in  principle  a  large  thermometer,  in  the  bulb 
of  which  combustion  takes  place,  the  heat  being  absorbed 
by  the  liquid  which  is  within  the  bulb.  The  absorption 
of  heat  is  proportional  to  the  height  to  which  a  column  of 
liquid  rises  in  the  attached  glass  tube. 

Q.  How  may  a  copper  -  ball  calorimeter,  suitable  for 
ascertaining  smoke-box  temperatures,  be  made  ? 

At  the  Purdue  University  such  a  calorimeter  is  employed 
in  locomotive  tests,  and  is  constructed  as  follows : 

A  piece  of  i-inch  steam  pipe,  threaded  at  one  end,  is 
screwed  through  the  shell  from  the  inside  of  the  smoke 
box.  It  is  set  radially  about  4  inches  from  the  front  tube 
sheet,  and  inclines  from  the  centre  of  the  smoke  box  down- 
ward. The  threaded  end  passes  through  the  shell  a  suffi- 
cient distance  to  receive  a  cap.  The  cap  serves  to  close 
the  end  of  the  pipe,  and  also  to  carry  a  light  rod,  to  the 
opposite  end  of  which  is  attached  a  simple  piston  fitting 
loosely  to  the  bore  of  the  pipe.  A  copper  ball,  fa  inch  in 
diameter,  and  a  copper  vessel  suitably  enclosed  to  prevent 
radiation,  complete  the  outfit.  In  using  the  apparatus,  the 
copper  ball  is  inserted  in  the  bore  of  the  pipe,  the  piston 
applied  below  it,  and  both  are  pushed  up  the  pipe  until  the 
cap  at  the  lower  extremity  of  the  piston  rod  meets  the 
lower  end  of  the  pipe.  The  cap  is  then  screwed  in  place, 
closing  the  pipe  and  retaining  the  ball  at  the  centre  of  the 


194  COMBUSTION   OF   COAL. 

smoke  box.  Here  it  is  allowed  to  remain  from  40  to  60 
minutes,  after  which  interval  it  is  assumed  to  have  come 
to  the  temperature  of  the  smoke  box.  The  cap  is  then 
unscrewed  and  the  piston  quickly  withdrawn,  allowing  the 
ball  to  roll  down  the  pipe  into  the  water  contained  in  the 
copper  vessel.  From  the  known  weight  of  the  ball,  the 
water,  and  the  copper  vessel,  and  from  observed  changes 
in  temperature,  the  original  temperature  of  the  ball  is  cal- 
culated. The  average  result  of  three  such  determinations 
is  assumed  to  be  the  temperature  of  the  smoke  box  for  the 
test. 

Q.  Is  the  amount  of  heat  evolved  by  combustion  in 
proportion  to  the  amount  of  oxygen  consumed? 

In  the  erroneous  belief  that  the  amount  of  heat  evolved 
on  combustion  was  in  proportion  to  the  amount  of  oxygen 
consumed,  Berthier  determined  the  calorific  power  of 
fuel  by  burning  it  by  the  oxygen  contained  in  oxide  of 
lead,  PbO,  and  ascertaining  the  weight  of  the  resulting 
button  of  lead. 

The  calorific  powers  of  various  fuels  as  thus  determined 
are  as  follows : 

<*•*••  he^unt, 

Air-dried  wood  with  20%  H2O    2,800  5,040 

Charred  wood 3, 600  6,480 

Wood  charcoal  with  20$  II 2O 6,000  10,  800 

Dry  charcoal 7.050  12,690 

Peat  with  20$  H2O 3, 600  6.480 

Dried  peat 4, 800  8,640 

Peat  charcoal 5, 800  10,440 

Average  bituminous  coal 7,  500  13,  500 

Good  coke 7, 050  1 2, 690 

Coke  with  5^  ash 6,  ooo  10, 800 

4,360  7,848 


Air-dried  lignite to  . 

(    5,410  9,738 

Hydrogen 34, 462  62, 032 

Carbon  burnt  to  CO 2,473  4,451 


BERTHIER  S    CALORIMETER. 


195 


Calories. 

Carbon  burnt  to  CO2 8, 080 

CO,  burnt  to  CO2 2,403 

Marsh  gas , 1 3, 063 

Olefiant  gas 11,858 


British 
heat  units. 

14,  544 

4,325 

23.513 

21,344 


Q.  What  is  the  Berthier  method  of  coal  calorimetry  ? 

The  apparatus  consists  of  gas  furnace  and  crucible 
clearly  shown  in  Fig.  17,  which  are  so  simple  as  to  be  self- 
explanatory.  Berthier 's  method  of  coal  calorimetry  uses 


FIG.  17. 


oxide  of  lead,  PbO,  as  the  source  of  oxygen.  It  requires 
only  accurate  weighing  of  the  sample  of  fuel  and  an  easily 
controllable  fire  for  heating  a  clay  crucible  to  a  low  red 
heat.  There  are  no  corrections  for  radiation  and  no  deli- 
cate measurements  of  temperature  to  be  made.  These  are 
apparently  the  great  sources  of  error  in  the  use  of  oxygen 
gas. 

The  heating  power  of  fuels  may  be  ascertained  by  mix- 
ing intimately  i  part  by  weight  of  the  substance,  in  the 
finest  state  of  division,  with  at  least  20,  but  not  more  than 


196 


COMBUSTION    OF   COAL. 


40,  parts  of  litharge.  Charcoal,  coke,  or  coal  may  be 
readily  pulverized;  but  in  the  case  of  wood  the  sawdust 
produced  by  a  fine  saw  or  rasp  must  be  employed.  The 
mixture  is  put  into  a  close-grained  conical  clay  crucible, 
and  covered  with  20  or  30  times  its  weight  of  pure  litharge. 
The  crucible,  which  should  not  be  more  than  half  full,  is 
covered  and  then  heated  gradually  until  the  litharge  is 
melted  and  evolution  of  gas  has  ceased.  At  first  the  mix- 
ture softens  and  froths.  When  the  fusion  is  complete,  the 
crucible  should  be  heated  more  strongly  for  about  ten  min- 
utes, so  that  the  reduced  lead  may  thoroughly  subside  and 
collect  into  one  button  at  the  bottom.  Care  must  be  taken 
to  prevent  the  reduction  of  any  of  the  litharge  by  the  gases 
of  the  furnace.  The  crucible,  while  hot,  should  be  taken 
out  of  the  fire  and  left  to  cool ;  when  cold,  it  is  broken, 
and  the  button  of  lead  detached,  cleaned,  and  weighed. 
The  accuracy  of  the  result  should  be  tested  by  repetition. 

TABLE  25. — COMPARISON  OF  OXYGEN  AND  LITHARGE  METHODS. 


Fuel. 

WEIGHT  OF 
FUEL,  GRAMS. 

HEATING 
POWER. 

RESULTS. 

PROBABLE 
ERROR 
PER  CENT. 

Oxy. 

Lith. 

Oxy. 

Lith. 

Oxy. 

Lith. 

Oxy. 

Lith. 

1 
Carbon     from 
gran  u  1  a  t  e  d  J 
sugar.     Ash, 
0.44$  

.... 

2.18 
1.882 
1.879 
2.767 
2.919 

1-937 
3-197 
2.306 

3-453 
3-502 
2.877 
2.4535 
2.3165 

2.OOOO 
2.OOOO 
2.9675 

| 

2 

gj 

3 

14,720 
14,090 
14,520 
14,320 
15,460 
12,660 
12,370 
12,520 
12,230 
14,000 

14,640 
14,800 
14,550 
13,920 
13,590 
14,480 
11,420 
11,530 
11,400 
11,520 
11,420 
13,560 
13,650 
13,604 
13,622 
13,643 

a 

3 

1 

"rt 
L> 

14,620 
12,760 

All. 

14,330 

1,2,3.6 
14,617 

11,470 

13,616 

9Det. 
±2.6 

±  I.I 

±  1-7 

ODet. 

±  o.  76 

±  0.14 
±  0.08 

Bituminous 
slack    f  r  o  m  - 
West     V  i  r  - 
ginia 

•  310 

•  377 
.468 
.204 
.812 
.328 
•372 
•394 
•  538 
.262 

Anthracite  coal 
from  Lehigh- 
Valley  

CALORIFIC   VALUE    OF    WOOD.  197 

The  purpose  of  covering  the  mixture  of  fuel  and  litharge 
in  the  crucible  with  a  quantity  of  pure  litharge  is  not  only 
to  prevent  access  of  air  to  the  fuel,  but  also  to  prevent  the 
escape  unoxidized  of  the  more  volatile  portions  of  the  fuel. 
And  this  covering  of  pure  litharge  must  likewise  be  pro- 
tected from  the  furnace  gases.  This  apparatus  is  fully 
described  in  theoretical  detail  by  C.  V.  Kerr,  Trans.  A. 
S.  M.  E.,  1899. 

Q.  What  is  the  calorific  value  of  wood  ? 

The  large  percentage  of  moisture  in  wood  renders  it  un- 
suitable as  fuel  where  high  temperatures  are  required. 
The  hydrogen  present  in  wood  is  not  available  as  fuel  owing 
to  the  presence  of  oxygen,  these  two  gases  uniting  to  form 
water.  Carbon  is  the  only  combustible  available  in  wood 
for  generating  heat.  This  element  is  present  in  all  woods, 
averaging  about  50  per  cent  of  the  total  weight  when  dry. 

A  cord  of  wood  contains  128  cubic  feet;  its  weight  is 
about  2,700  pounds,  or  21  pounds  per  cubic  foot.  2.12 
cords,  or  2.55  tons  of  pine  wood,  were  found  to  be  equal  to 
i  ton  Cumberland  coal,  I  pound  of  the  latter  equalling 
2.55  pounds  of  wood.  In  evaporative  power  the  pine  wood 
had  but  two-fifths  of  that  of  coal,  equal  to  about  2)4  pounds 
of  water  evaporated  per  pound  of  pine.  This  is  much  less 
than  the  results  obtained  by  Prof.  W.  R.  Johnson  in  1844, 
who  found  that  I  pound  of  dry  pine  would,  by  careful 
management,  evaporate  4.69  pounds  of  water. 

The  American  Society  of  Mechanical  Engineers,  in  their 
rules  for  boiler  tests,  assume  one  pound  of  wood  to  equal 
0.4  pound  of  coal. 

Q.  How  does  wood  compare  with  cotton  stalks,  brush- 
wood, or  straw  as  a  fuel  ? 

The  evaporative  values,  given  by  John  Head,  for  the 


198  COMBUSTION  OF  COAL. 

following  substances,  when  burnt  in  a  tubular  boiler,  com- 
pare as  follows : 

Eight  pounds  of  water  evaporated  by  I  pound  good  coal ; 
2  pounds  dry  peat;  2.25  to  2.3  pounds  dry  wood;  2.5  to  3 
pounds  cotton  stalks  or  brushwood;  3.25  to  3.75  pounds 
straw. 

Q.  What  is  the  calorific  value  of  peat? 

Very  little  use  has  been  made  of  peat  in  this  country, 
owing  to  the  abundance,  cheapness,  and  superior  heating 
power  of  bituminous  coal.  Carefully  conducted  tests 
abroad  show  that  peat,  air-dried,  containing  not  more  than 
14  per  cent  of  moisture,  has  about  one-half  the  evaporative 
power  of  good  coal,  and  is  superior  to  that  of  ordinary  air- 
dried  wood. 

The  calorific  power  of  peat  varies  from  5,400  heat  units 
for  ordinary  air-dried  peat,  to  9,400  heat  units  per  pound 
when  thoroughly  dry.  This  corresponds  to  an  evaporation, 
from  and  at  212°  F.,  of  5.6  pounds  of  water  for  the  for- 
mer, and  9.79  pounds  for  the  latter. 

Q.  What  is  the  calorific  value  of  lignite  ? 

Freshly  mined  lignite  contains  an  excess  of  moisture,  to 
which  is  generally  attributed  its  low  heating  power.  The 
large  amount  of  volatile  combustible  matter  contained  in 
lignite  causes  it  to  burn  with  a  long  smoky  flame.  The 
calorific  value  of  lignites  will  vary  from  6,500  to  11,000 
heat  units,  and  occasionally  higher  for  the  better  qualities. 
This  is  equal  to  an  equivalent  evaporation  from  and  at 
212°  F.  of  6.73  pounds  of  water  for  the  former,  and  1 1.38 
pounds  for  the  latter. 

Q.  What  is  the  calorific  value  of  bituminous  coal? 

The  calorific  value  of  bituminous  coal  for  the  lower 
grades  depends  almost  wholly  upon  the  amount  of  its  fixed 


CALORIFIC  VALUE  OF  COKE.         199 

carbon,  the  moisture  and  excess  of  oxygen  operating 
against  the  efficiency  of  the  fire  as  a  whole ;  some  of  the 
lower  grades  of  coal  developing  not  more  than  8,000  heat 
units,  corresponding  to  an  equivalent  evaporation  of  8.28 
pounds  of  water  from  and  at  212°  F.  per  pound  of  coal. 

The  better  grades  of  bituminous  coal  develop  from  13,- 
ooo  to  14,500  heat  units  per  pound  of  coal,  corresponding 
to  an  equivalent  evaporation  of  13.45  pounds  of  water  for 
the  former,  and  15.01  pounds  for  the  latter,  both  from  and 
at  212°  F. 

A  good  average  for  the  best  varieties  of  bituminous  coal 
is  13,600  heat  units,  corresponding  to  an  evaporation  of 
14.08  pounds  of  water  from  and  at  212°  F.  per  pound  of 
coal. 

Q.  What  is  the  calorific  value  of  coke  ? 

The  calorific  power  of  coke  should  be  very  high,  inas- 
much as  it  is  nearly  pure  carbon.  Deducting  the  ash  and 
other  impurities,  coke  should  yield  12,500  to  13,800  heat 
units  per  pound,  which  corresponds  to  an  equivalent  evap- 
oration of  12.94  pounds  of  water  for  the  former,  and  14.28 
pounds  for  the  latter,  from  and  at  212°  F.  per  pound  of 
coke. 

D.  K.  Clark  states  that  the  best  experience  of  the  com- 
bustion of  coke  has  been  derived  from  the  practice  of  loco- 
motives. A  rapid  draught  is  required  for  effecting  the 
complete  combustion  of  coke,  preventing  the  reaction 
which  is  likely  to  take  place  when  currents  of  carbonic 
acid  traverse  ignited  coke,  and  convert  it  into  carbonic 
oxide.  He  showed  by  a  process  of  mechanical  analysis 
that  the  combustion  of  coke  in  the  fire  box  of  the  ordinary 
coal-burning  locomotive  was  complete.  The  total  heat  of 
combustion  of  one  pound  of  good  sound  coke  was  found 


20O  COMBUSTION   OF   COAL. 

ordinarily  to  be  disposed  of  as  follows,  when  the  tempera- 
ture in  the  smoke  box  did  not  exceed  600°  F.  :  78.0  per 
cent  in  the  formation  of  steam;  16.  5  per  cent  by  the  heat 
of  burnt  gases  in  smoke  box;  5.5  per  cent  drawback  by 
ash  and  waste. 

Q.  What  is  the  calorific  value  of  anthracite  coal  ? 

Anthracite  coals  are  principally  carbon  and  ash.  Ex- 
cluding the  moisture,  there  is  not  enough  available  hydro- 
gen in  the  volatile  matter  to  be  of  any  heating  value,  after 
deducting  the  energy  required  to  dissociate  the  volatile 
combustible  from  the  fixed  carbon.  The  volatile  combus- 
tible may,  therefore,  be  wholly  neglected  without  sensible 
loss,  and  the  coal  treated  according  to  its  percentage  of 
carbon. 

Beaver  Meadow,  Carbon  County,  Pa.,  anthracite  coal 
(Geol.  Surv.,  Pa.). 

Specific  gravity,  1.55  =  96.88  pounds  per  cubic  foot. 

Fixed  carbon  ................................  90.  20  per  cent. 

Volatile  matter  ..............................     2.52 

Earthy  matter,  ash  ...........................     6.  13       " 

98-85       " 

Neglecting  the  1.15  per  cent  loss  in  the  analysis,  we 
have  as  the  calorific  power  of  this  fuel  : 

Carbon  .......................  9020X14,  544=  13,  H9 

Volatile  matter  .................  0252  X  20,  115  =  507 

Less  ..........................  0252  X    3-600=    91=       416 

Total  heat  units  ..........................  ........  13-535 

Then  :        jjf    —  14.01  pounds  of  water  evaporated  per 


pound  of  coal  from  and  at  212°  F. 


CHAPTER  IX. 

STEAM    GENERATION. 

Q.  What  is  the  nature  of  the  heat  problem  in  a  steam 
engine  ? 

It  is  to  convert  the  heat  generated  in  the  furnace  by  the 
combustion  of  fuel  into  the  sensible  motion  of  ponderable 
masses— a  piston,  fly  wheel,  etc. ;  and  the  degree  in  which 
it  is  possible  for  it  to  accomplish  this  (every  imperfection 
and  every  source  of  loss  eliminated)  is  the  ratio  which  the 
difference  of  temperature  of  initial  and  exhaust  steam  (or 
its  range)  bears  to  the  absolute  temperature  of  initial 

T  —  T 

steam ;  that  is,  -  °         ',  where  T0  is  the  absolute  initial 

temperature,  and  T,  the  absolute  final  temperature. 

Example :  Suppose  a  locomotive  takes  steam  up  to  the 
point  of  cut  off  at  120  pounds  gauge  pressure,  to  which 
we  add  the  pressure  of  the  atmosphere,  14.7  pounds--  1 34.7 
pounds  absolute  pressure ;  its  sensible  temperature  would 
be  350°  F.  and  its  absolute  temperature  461°  more,  or 
3  50° +  461°  =  8 11°.  If  this  steam  be  exhausted  under 
pressure  a  little  greater  than  that  of  the  atmosphere,  say 
15  pounds  absolute,  its  sensible  temperature  would  be 
213°  F.,  and  its  absolute  temperature  461°  more,  or 
674.°  Now  if  T0  =  8 1 1°,  and  T,  =  674,°  we  have  : 
TV- jr,  _  811-674  _  137  _ 

To  811         -  811  ~ 

or  say  16.9  per  cent.     That  is,  the  range  of  temperature 


202  COMBUSTION    OF   COAL. 

between  initial  and  exhaust  steam  being  137°  F. ,  and  the 
absolute  initial  temperature  being  811°  F.,  such  a  steam 
engine,  on  account  of  being  obliged  to  let  the  steam  go 
while  it  still  has  a  temperature  of  213°  F.  or  674°  abso- 
lute, has  within  its  reach,  if  it  could  save  it  all,  only  16.9 
per  cent  of  the  whole  work  contained  in  the  initial  steam 
in  the  form  of  heat.  Such  an  engine  will  in  fact  yield 
about  6  per  cent;  and  dividing  this  6  per  cent  by  the  16.9 

6 
per  cent  we  have  — ^—  =  .355,  or  35.5  per  cent.,  as  the 

ratio  of  usual  engine  performance  to  perfect  performance  of 
perfect  heat  engine  under  the  above  usual  conditions. 
About  two-thirds,  then,  of  the  heat  work  that  may  at  least 
be  striven  for  is  usually  lost  (Hoadley). 

Q.  What  is  meant  by  the  range  of  temperature  in  a 
steam  engine  ? 

It  is  the  difference  between  the  temperature  of  the  steam 
entering  the  cylinder  and  the  temperature  of  its  exhaust. 
These  temperatures  should  be  expressed  in  terms  of  the 
absolute  scale  of  temperatures,  and  not  that  of  the  ordinary 
thermometer. 

Q.  Does  water  conduct  heat  readily  ? 

Water  conducts  heat  very  slowly  from  above  downward. 
The  effect  observed  is  very  different  when,  instead  of  ap- 
plying heat  at  the  upper  surface,  it  is  communicated  to  the 
under  part,  or  to  the  bottom  of  a  vessel  in  which  liquid  is 
contained.  In  this  case  the  particles  in  immediate  contact 
with  the  heat-giving  body  are  expanded.  This,  by  render- 
ing them  lighter  than  the  succeeding  ones,  causes  them  to 
ascend;  fresh  particles  succeed,  and  these  rise  in  similar 
manner.  Currents  are  thus  determined  in  the  liquid,  and 
the  whole  mass  is  readily  heated.  This,  however,  is  not 


LATENT  HEAT  OF  EVAPORATION.        203 

a  case  of  conduction  from  particle  to  particle ;  neither  is 
it  due  to  radiation,  but  it  is  the  effect  of  convection — that 
is  to  say,  the  actual  conveyance  or  distribution  of  the  heated 
portion  throughout  the  mass. 

Q.  What  is  the  limiting  difference  in  temperature  be- 
tween the  heated  gases  in  contact  with  a  steam  boiler, 
and  the  temperature  of  the  steam  within  ? 

A  common  steam  pressure  in  stationary  boilers  is  80 
pounds  by  gauge,  or  95  pounds  absolute,  the  correspond- 
ing temperature  being  324°  F.,  which  represents  the  cool- 
ing surface  to  which  the  hot  furnace  gases  are  exposed. 
It  is  probable  that  there  can  be  no  active  transmission  of 
heat  from  the  gases  without  to  the.  water  within  a  boiler, 
with  less  than  75°  F.  difference  of  temperature.  Pyrom- 
eter observations  made  by  Hoadley,  in  the  smoke  box  of  a 
return  tubular  boiler,  at  all  stages  of  the  fire,  satisfied  him 
that  in  excellent  boilers,  well  fired,  having  a  ratio  of  heat- 
ing surface  to  grate  area  as  large  as  36,  the  temperature  of 
the  escaping  gases  rarely,  if  ever,  falls  lower  than  75°  F. 
above  the  temperature  due  to  the  steam  pressure,  except 
when  the  fire  doors  are  open  and  there  is  great  and  un- 
usual excess  of  air  admitted.  Adding  75°  to  the  tempera- 
ture corresponding  to  80  pounds  gauge  pressure,  324°,  we 
have,  say,  400°  F.  as  the  lowest  practical  temperature  of 
escaping  gases.  This  will  be  confirmed  by  the  best  prac- 
tice under  favorable  conditions ;  and  the  actual  tempera- 
ture will  range  through  a  low  average  of  500°  F.  and  a 
high  average  of  600°  F.  up  to  800°  F.  or  over. 

Q.  What  is  the  latent  heat  of  evaporation  ? 

When  water  has  been  raised  to  a  temperature  of  212°  F. 
in  a  vessel  open  to  the  atmosphere,  the  continued  applica- 
tion of  heat  does  not  cause  a  further  rise  in  temperature. 


204  COMBUSTION   OF   COAL. 

It  will  be  observed  that  much  more  heat  is  required  to 
evaporate  a  given  quantity  of  water  from  and  at  212°  than 
was  necessary  to  bring  its  temperature  up  to  the  boiling 
point. 

The  quantity  of  heat  required  to  evaporate  i  pound  of 
water  from  and  at  212°  has  been  experimentally  shown  to 
be  equal  to  966  British  thermal  units. 

The  total  heat  in  I  pound  of  steam  at  212°  F.  is  1 146 
units,  of  which  212°  -  32°  =  180°  are  necessary  to  bring 
the  water  from  the  freezing  to  the  boiling  point ;  and  966 
units  of  heat  per  pound  of  water  are  expended  in  doing  the 
internal  work  of  pulling  the  liquid  molecules  asunder,  to 
which  must  also  be  added  the  exterior  work  of  forcing 
back  the  atmosphere  when  the  liquid  becomes  vapor. 

The  heat  thus  expended  in  the  conversion  of  water  into 
steam  from  and  at  212°  F.,  viz.,  966  heat  units  per  pound 
of  water,  and  of  which  the  thermometer  gives  no  record,  is 
the  latent  heat  of  evaporation. 

Q.  How  may  the  latent  heat  in  steam  be  proven  by 
the  quantity  of  water  required  for  its  condensation  ? 

If  the  feed  water  and  the  water  for  condensation  are  60° 
F.,  the  water  leaving  the  condenser  at  120°  F.,  the  steam 
being  condensed  from  212°  F. ,  we  have :  Total  heat  in 
one  pound  of  steam  from  water  at  32°  =  1,146  heat  units. 

The  water  entering  the  boiler  at  60°  instead  of  32°, 
there  is  a  gain  of  60  —  32  =  28°,  the  heat  expended  being 
1 146  —  28  =  1 1 1 8  heat  units.  Subtracting  the  tempera- 
ture of  the  injection  from  that  of  the  discharge  water 
we  have  :  1 20  —  60  =  60°  difference.  Then  1 1 1 4  -f-  60 
=  18.63  times  as  much  water  required  to  condense  the 
steam  as  was  evaporated  to  make  it.  In  practice,  25  times 
is  the  usual  allowance. 


FACTOR    OF    EVAPORATION.  2O5 

Q.  Is  the  latent  heat  of  evaporation  wholly  lost  in 
steam  engineering  practice? 

In  the  case  of  non-condensing  engines  exhausting  di- 
rectly into  the  atmosphere,  the  latent  heat  contained  in 
the  steam  is  lost ;  and  this  is  the  principal  loss  which  oc- 
curs in  the  steam  engine  when  considered  as  a  heat  engine. 

In  a  condensing  engine  a  partial  recovery  of  this  loss  is 
had  by  the  condensation  of  the  exhaust  steam,  and  conse- 
quent utilization  of  the  pressure  of  the  atmosphere  upon 
the  engine  piston  corresponding  to  the  vacuum  obtained, 
from  which  must  be  deducted  the  quantity  of  work  ex- 
pended in  operating  the  air  pump. 

Q.  What  is  meant  by  factor  of  evaporation? 

A  factor  of  evaporation  is  found  by  subtracting  the 
temperature  of  the  feed  water  above  32°  F.  from  the  total 
heat  in  steam  above  32°  F.  at  its  pressure  above  vacuum, 
and  dividing  the  remainder  by  966,  or  the  latent  heat  of 
steam  at  atmospheric  pressure.  It  is  commonly  expressed 
by  the  formula : 

Factor  of  evaporation  =  — ^-,  in  which  H  and  h  are 

respectively  the  total  heat  in  steam  of  the  average  observed 
pressure,  and  in  water  of  the  average  observed  temperature 
of  the  feed. 

If  we  suppose  water  to  enter  a  boiler  at  70°  F. ,  the  steam 
pressure  to  be  100  pounds  by  gauge  or  1 15  pounds  abso- 
lute, the  factor  of  evaporation  would  be  found  thus : 

The  total  heat  in  steam  above  32°  F.  at  1 15  pounds  ab- 
solute =  1 185. 

Temperature  of  feed,  70°  —  32°  =  38. 

1185  —.38 
factor  ot  evaporation  =  -  — 'L- :  -  =  1.187 


2O6 


COMBUSTION   OF   COAL. 


A  table  of  factors  of  evaporation  is  here  given  for  steam 
pressures  by  gauge  from  60  to  200  pounds  per  square  inch, 
varying  by  10  pounds,  together  with  feed  water  tempera- 
tures from  32°  to  210°,  varying  by  10°  F. 

The  use  of  the  table  will  be  illustrated  in  the  solution 
of  the  following  example  : 

Suppose  a  boiler  to  evaporate  9  pounds  of  water  per 
pound  of  coal,  the  feed  water  entering  at  70°  F.,  the  steam 
pressure  to  be  100  pounds  by  gauge,  what  is  the  equiva- 
lent evaporation  from  and  at  212°? 

The  factor  of  evaporation  corresponding  to  the  steam 
pressure  and  temperature  of  feed  water  shown  in  Table  26 
is  1.187,  which  multiplied  by  the  pounds  of  water  evapo- 
rated will  be:  1.187  X9  =  10.683  pounds  of  water  per 
pound  of  coal. 

TABLE  26. — FACTORS  OF  EVAPORATION. 


8*8? 

STEAM  PRESSURE  BY  GAUGE. 

H!« 

60 

70 

80 

90 

loo 

110 

120 

130 

140 

150 

160 

170 

1  80 

190 

200 

32 

.216 

.220 

1.222 

.225 

t.227 

.229 

I.23I 

1.232 

•234 

1.236 

•237 

1.239 

.240 

241 

•243 

40 

.209 

.212 

I.2I4 

.216 

I.2I9 

.220 

1.222 

1.224 

.226 

1.227 

.220 

1.230 

-232 

233 

.234 

50 

-IQ7 

.201 

1.204 

.206 

1.  208 

.2IO 

1.  212 

1.214 

.21S 

.217 

.218 

1.220 

.221 

225 

.224 

60 

.188 

.191 

I-I93 

.196 

I.I98 

.200 

1.202 

1.203 

.205 

.207 

.208 

I.2IO 

.211 

212 

.214 

70 

.178 

.l8o 

.185 

1.187 

.I8Q 

I.I9I 

1.193 

.194 

.197 

1.199 

.200 

202 

203 

80 

.167 

.170 

I-I73 

I.I77 

.179 

I.lSl 

1.183 

.I84 

.186 

.187 

1.189 

.190 

192 

193 

90 

.160 

I.l62 

.165 

1.167 

.169 

I.I70 

1.172 

.174 

.176 

.177 

I.I79 

.180 

181 

100 

•147 

.150 

1.152 

•154 

1.156 

.IS8 

1.160 

1.162 

.164 

.165 

.l67 

1.168 

.170 

171 

172 

no 

.136 

•139 

I.I42 

.144 

1.146 

.148 

1.150 

1.152 

•T53 

-1,56 

1.158 

•159 

160 

162 

120 

.126 

.129 

I.I3I 

1.136 

.138 

1.140 

1.141 

•T43 

.145 

.I46 

I.I47 

I.I49 

150 

15! 

130 

.116 

.118 

1.  121 

.123 

t.125 

.127 

1.129 

1.130 

.132 

•134 

.136 

I-I37 

I.I38 

140 

141 

140 

.105 

.108 

1.  100 

I.II5 

.117 

1.119 

1.  120 

.122 

.124 

.125 

I.I27 

4.128 

129 

^3* 

15° 

•°95 

.098 

I.1OO 

.102 

I.I04 

.106 

1.108 

i.  no 

.III 

•"3 

."5 

1.116 

1-IlS 

119 

1  20 

160 

.084 

.087 

1.090 

.092 

1.094 

.096 

1.098 

I.IOO 

.101 

.103 

.104 

1.  106 

J.107 

108 

110 

170 

.074 

.077 

1.079 

1.081 

1.083 

1.085 

1.087 

1.089 

.091 

.092 

.094 

1.095 

1.097 

098 

099 

1  80 

.063 

.066 

1.069 

1.071 

1-073 

1-075 

1.077 

1.079 

.080 

.082 

.083 

1.085 

1.  086 

088 

089 

190 

200 

•053 
-04S 

.056 
045 

1.058 

1.0,8 

i.  060 
1.050 

1.063 
I.OS2 

1.065 
1.054 

i.  066 
1.056 

i.  068 
1.058 

.070 

.059 

.071 
.061 

.073 
.063 

I>074 
1.064 

1.076 
1.065 

T 
.067 

078 
068 

2IO 

1.032 

'•035 

1-037 

1.040 

I.O42 

1.044 

1.046 

1.047 

.049 

1.051 

.052 

1-053 

1-055 

.051 

057 

Factors  of  equivalent  evaporation  show  the  proportionate 
cost  in  heat  or  fuel  of -producing  steam  at  any  given  press- 
ure as  compared  with  atmospheric  pressure.  To  ascer- 


TOTAL    HEAT    IN    STEAM. 


207 


tain  the  equivalent  evaporation  at  any  pressure,  multiply 
the  given  evaporation  by  the  factor  of  its  pressure,  and  di- 
vide the  product  by  the  factor  of  the  desired  pressure. 

Each  degree  of  difference  in  temperature  of  feed  water 
makes  a  difference  of  .00104  in  the  amount  of  evaporation. 
Hence  to  ascertain  the  equivalent  evaporation  from  any 
other  temperature  of  feed  than  212°,  add  to  the  factor  given 
as  many  times  .00104  as  the  temperature  of  feed  water  in 
degrees  below  2 1 2°.  For  other  pressures  than  those  given 
it  will  be  practically  correct  to  take  the  proportion  of  the 
difference  between  the  nearest  pressures  in  Table  27, 
adapted  from  table  published  by  Babcock  &  Wilcox  Com- 
pany. 

TABLE  27. — FACTOR  OF  EQUIVALENT  EVAPORATION  AT  212°  F. 


Total  pressure  above 
vacuum  in  pounds  per 
square  inch. 

Factor 
of  equivalent 
evaporation  at 

212°. 

Total  pressure  above 
vacuum  in  pounds  per 
square  inch. 

Factor 
of  equivalent 
evaporation  at 

212°. 

15       .         

.0003 

GO  

.O35O 

2O 

OOCT 

QC 

.0^62 

oc 

OOQQ 

100  

.O374 

-5Q 

OI2Q 

105 

.O385 

•je 

.01^7 

no  

.O3Q6 

4O 

.Ol82 

115       

.O4O6 

1C 

O2O5 

I  2O         ... 

O4l6 

en 

O22C, 

128 

.O426 

e  e 

O24C, 

I  -JO 

.04^*5 

60 

.O263 

I4O 

.O453 

6^ 

O28O 

ICQ 

.O47O 

7O 

.0205 

160         

.O486 

7c 

.O^OQ 

1  70  

.O5O2 

so          .... 

I.O*?23 

180  

.O5I7 

85  

1.0337 

Q.  What  is  meant  by  total  heat  in  steam  ? 

The  total  heat  in  steam  includes  the  sensible  tempera- 
ture of  the  steam  above  32°,  plus  the  latent  heat  of  evapo- 
ration corresponding  to  the  pressure  under  which  the  steam 
is  generated. 


208 


COMBUSTION   OF   COAL. 


TABLE  28. — PROPERTIES  OF    SATURATED  STEAM,  PRESSURE,  TEMPERA- 
TURE, VOLUME  AND  DENSITY.     (Haswell's  Table. ) 


Pressure 
per 
square  inch, 
pounds. 

Pressure 
in  mercury, 
inches. 

Tem- 
perature, 
degrees. 

Total  heat 
from  water  at 
32°. 

Volume 
of  one  pound, 
cubic  feet. 

Density, 
or  weight  of 
one  cubic  foot, 
pounds. 

I 

2.O4 

102.  1 

III2.5 

330.36 

.003 

5 

10.18 

162.3 

H30.9 

72.66 

.0138 

10 

20.36 

193.3 

II40.3 

37-84 

.0264 

14.7 

29.92 

212 

1146.1 

26.36 

.03802 

20 

40.72 

228 

II50.9 

19.72 

.0507 

25 

50.9 

24O.I 

II54-6 

15-99 

.0625 

30 

61.08 

250.4 

II57-8 

13.46 

•0743 

35 

71.26 

259-3 

1160.5 

11.65 

.0858 

40 

81.43 

267.3 

1162.9 

IO.27 

.0974 

45 

91.61 

274.4 

1165.1 

9.18 

.1089 

50 

101.8 

281 

1167.1 

8.3I 

.1202 

55 

111.98 

287.1 

1169 

7.6l 

.1314 

60 

122.16 

292.7 

II70.7 

7.01 

.1425 

65 

132.34 

298 

II72.3 

6.49 

.1538 

70 

142.52 

302.9 

II73.8 

6.07 

.1648 

75 

152.69 

307.5 

H75.2 

5.68 

-1759 

80 

162.87 

3I2 

1176.5 

5-35 

.1869 

85 

173-05 

3I6.I 

II77.9 

5-05 

.198 

90 

183.23 

320.2 

II79.I 

4.79 

.208g 

95 

193-41 

324.1 

II80.3 

4-55 

.2198 

100 

203.59 

327.9 

Il8l.4 

4-33 

.2307 

105 

213-77 

331-3 

1182.4 

4.14 

.2414 

no 

223.95 

334.6 

H83.5 

3-97 

.2521 

H5 

234.13 

338 

II84.5 

3.8 

.2628 

120 

244-  3  i 

34LI 

1185.4 

3-65 

.2738 

125 

254-49 

344-2 

1186.4 

3-51 

.2845 

130 

264.67 

347-2 

1187.3 

3.38 

•2955 

135 

274.85 

350.1 

II88.2 

3-27 

.306 

140 

285.03 

352.9 

1189 

3.16 

.3162 

145 

295.21 

355-6 

1189.9 

3.06 

.3273 

149 

303.35 

357-8 

II90.5 

2.98 

•  3357 

150 

305.39 

358.3 

1190.7 

2.96 

.3377 

155 

315.57 

361 

II9I.5 

2.87 

.3484 

1  60 

325.75 

363-4 

II92.2 

2-79 

•  359 

165 

335.93 

366 

1192.9 

2.71 

.3695 

170 

346.  1  1 

368.2 

II93-7 

2.63 

.3798 

175 

356.29 

370.8 

1194.4 

2.56 

•3899 

1  80 

366.47 

372-9 

II95.I 

2-49 

.4009 

185 

376.65 

375-3 

II95-8 

2.43 

.4117 

I90 

386.83 

377-5 

II96.5 

2.37 

.4222 

195 

397-01 

379-7 

II97.2 

2.31 

.4327 

200 

407.19 

38i.7 

II97.8 

2.26 

•4-131 

TOTAL   HEAT   IN   STEAM.  2CK) 

At  atmospheric  pressure  we  have  :  212°  F.,  the  sensible 
temperature  of  steam ;  966  heat  units,  the  latent  heat  of 
evaporation.  Then 

212  —  32  =  ISO 

Latent  heat  =  966 


Total  heat  in  one  pound  of  steam  =  1146  heat  units. 

The  amount  of  heat  absorbed  in  vaporization,  or  rendered 
latent  by  each  pound  of  water  in  its  conversion  into  steam, 
varies  according  to  the  pressure  at  which  the  steam  is  gen- 
erated, being  greatest  at  atmospheric  pressure  and  de- 
creasing as  the  steam  pressure  increases.  For  example  : 

At  100  pounds  gauge  pressure  or  1 15  pounds  absolute 
we  have  a  corresponding  temperature  of  338°  F.  The 
latent  heat  of  vaporization  at  this  temperature  and  pressure 
is  876  units  of  heat  per  pound  of  water  evaporated.  We 
have  then : 

Temperature  of  the  steam  338  —  32  =  306 
Latent  heat  of  e vaporization  =  876 

Total  heat  in  steam  =  1182  British  ther.nal  units. 

A  result  which  varies  slightly  from  that  given  in  Table 
28.  As  the  tabular  numbers  are  those  obtained  by  direct 
experiment,  they  are  to  be  followed  in  all  cases. 

Q.  What  is  the  effect  of  the  withdrawal  of  heat  from 
steam  ? 

When  heat  is  withdrawn  from  steam  it  condenses  to 
form  water,  and  the  same  quantity  of  heat  necessary  to 
produce  the  steam  reappears  in  the  water  used  to  condense 
the  steam,  and  bring  it  back  to  the  original  temperature 
of  the  feed  water.  This  property  is  made  use  of  in  steam 
heating,  where  steam  of  very  low  pressure  is  made  to  give 
up  its  heat  through  the  sides  of  the  radiating  coils,  the 


2IO  COMBUSTION   OF   COAL. 

water  of  condensation  returning  to  the  boiler  at  a  temper- 
ature approximating  the  boiling  point,  depending  some- 
what on  the  details  of  the  piping. 

Q.  What  is  meant  by  evaporation  per  pound  of  com- 
bustible ? 

Evaporation  per  pound  of  combustible  is  the  net  evapo- 
ration per  pound  of  coal  after  making  due  allowance  for 
the  ashes  and  the  unburnt  coal  falling  through  the  grates. 

Suppose  1,000  pounds  of  coal  be  fed  to  the  furnace  and 
evaporated  8,  500  pounds  of  water,  this  would  be  an  evapo- 
ration of  8.5  pounds  of  water  per  pound  of  coal.  If  130 
pounds  of  ashes  remain  after  the  combustion  of  the  coal, 
we  have  :  1,000  —  130  =  870  pounds  of  combustible,  evapo- 
rating 8, 500  pounds  of  water.  The  evaporation  would 
then  be:  8,500  -=-  870  —  9.77  pounds  of  water  per  pound 
of  combustible. 

Q.  How  may  water  evaporated  per  pound  of  coal  be  con- 
verted into  equivalent  evaporation  from  and  at  212°  F. 
per  pound  of  combustible  ? 

Taking  a  case  from  actual  practice  in  which :  Steam 
pressure  by  gauge,  95  pounds ;  feed  water  entering  boiler, 
138°  F. ;  bituminous  coal;  coal  fed  to  the  furnace  deduct- 
ing moisture,  6,817  pounds;  ashes,  859  pounds;  total 
combustible,  5,958  pounds;  water  evaporated  per  pound 
of  coal,  9.04  pounds;  water  evaporated  per  pound  of  com- 
bustible, 10.34  pounds. 

Example  i.  What  is  the  equivalent  evaporation  from 
and  at  212°  per  pound  of  coal? 

Ninety-five  pounds  gauge  pressure  =  no  pounds  abso- 
lute. 

Heat  units  in  steam  1 1  o  pounds  absolute  pressure  from 
water  at  32°  =  1 183.5  (see  Table  28). 


EQUIVALENT    EVAPORATION.  2  I  I 

The  water  entering  the  boiler  at  138°  instead  of  32°, 
there  is  a  gain  of  138  —  32  —  106°. 

Then  :   1 183.  5  —  106  =  1077.  5  units  of  heat. 

Heat  units  in  steam         1077.5 

— - —     —  =  — r7—  —  1.115,  a  multiplier. 
Latent  heat  of  evap.          966 

9.04  X  1.115  —  10.08  pounds  of  water  evaporated  from 
and  at  212°  per  pound  of  coal. 

Example  2.  What  is  the  equivalent  evaporation  from 
and  at  212°  per  pound  of  combustible? 

Proceed  as  above  to  obtain  a  multiplier,  then  the  prod- 
uct of  the  water  evaporated  per  pound  of  combustible  into 
the  multiplier  will  be  the  answer,  thus  :  10.  34  X  1. 1 1 5  = 
11.54  pounds  of  water  evaporated  from  and  at  212°  per 
pound  of  combustible. 

Q.  What  is  meant  by  an  equivalent  evaporation  from 
and  at  212°  F.? 

Evaporation  from  and  at  212°  F.  takes  into  account  the 
latent  heat  of  evaporation.  The  rise  in  temperature  of 
the  feed  water  in  the  boiler  proceeds  regularly  with  each 
increment  of  heat  received  by  it,  until  the  temperature 
212°  is  reached,  at  which  point  the  water  continues  to 
receive  heat,  but  records  no  rise  in  temperature  until  966 
units  of  heat  have  been  absorbed  per  pound  of  water,  after 
which  the  thermometer  begins  to  record  higher  tempera- 
tures corresponding  to  the  pressure  of  steam. 

In  making  computations  from  and  at  212°  the  process 
is  divided  into  three  parts : 

1.  Heat  required  to  bring  feed  water  up  to  212°. 

2.  Heat  required  to  convert  one  pound  of  water  at  212° 
into  steam  at  212°  —  966  units. 

3.  Heat  in  steam  at  212°   F.,  or    1,146  units,  to  that 
corresponding  to  the  steam  pressure. 


212  COMBUSTION    OF   COAL. 

As  water  freezes  at  32°  F.  this  temperature  is  always 
to  be  deducted  from  the  temperature  of  the  feed. 

The  equivalent  evaporation  from  and  at  212°  is  found 
by  dividing  the  total  heat  in  the  steam  by  966,  which  gives 
a  multiplier  by  which  the  weight  of  water  actually  evapo- 
rated per  pound  of  coal  is  to  be  multiplied.  For  example  : 

A  boiler  evaporates  Sy2  pounds  of  water  per  pound  of 
coal  from  feed  water  at  75°  F.,  the  steam  pressure  being 
i oo  pounds  by  gauge  or  115  pounds  absolute.  What  is 
the  equivalent  evaporation  from  and  at  212°  F.  ? 

Referring  to  Table  28  we  find  the  total  heat  required 
to  generate  one  pound  of  steam  from  water  at  32°  under 
a  pressure  of  115  pounds  absolute  is  1184.5  neat  units. 
The  water  entering  the  boiler  at  75°  instead  of  32°,  there 
is  a  gain  of  75  —  32  =  43°.  Then  :  1 184.5  —  43  —  1 14I-S 

1 184.5 
units  of  heat;   — >.-  =  1.182,  the  multiplier ;  8.5  x  1.182 

QOO 

=  10.05  pounds,  the  equivalent  evaporation  from  and  at 
212°  at  atmospheric  pressure. 

Q.  How  may  the  equivalent  evaporation  from  and  at 
212°  be  estimated,  when  only  the  total  heat  of  combustion 
of  the  fuel  is  known? 

When  the  total  heat  of  combustion  of  one  pound  of  the 
combustible  is  known,  the  equivalent  evaporation  from  and 
at  212°  may  be  determined  by  dividing  the  number  of 
heat  units  required  to  convert  water  at  212°  into  steam  at 
atmospheric  pressure. 

Example :  Suppose  a  bituminous  coal  to  have  devel- 
oped by  calorimeter  test  13,200  heat  units  per  pound, 
what  would  be  the  equivalent  evaporation  from  and  at 

212°?  —    13.67    pounds    of     water,    at    atmos- 

900 

pheric  pressure. 


AVAILABLE    HEAT    OF    COMBUSTION.  213 

Q.  What  is  the  object  in  reducing  evaporative  results 
to  an  equivalent  evaporation  from  and  at  212°,  at  atmos- 
pheric pressure  ? 

Equivalent  evaporation  from  and  at  212°  F. ,  at  atmos- 
pheric pressure,  has  been  accepted  by  engineers  as  being 
at  once  the  readiest,  most  convenient,  and  most  intelligible 
basis  yet  suggested  for  estimating  the  comparative  evaporat- 
ing power  of  different  kinds  of  fuel.  It  represents  the 
weight  of  water  which  would  have  been  evaporated  by  each 
pound  of  fuel  had  the  water  been  both  supplied  and  evap- 
orated at  the  boiling  point  corresponding  to  the  mean  at- 
mospheric pressure. 

Q.  What  is  the  ordinary  rate  of  evaporation  per  pound 
of  small  anthracite  coal  when  burnt  in  horizontal  tubular 
boiler  furnaces  ? 

The  ordinary  rate  of  evaporation  per  pound  of  small  an- 
thracite coal,  from  feed  water  at  60°  F.,  under  80  pounds 
gauge  pressure,  say  324°  F.,  is  placed  by  Hoadley  as  be- 
ing in  general  below  8  pounds.  Indeed,  8  pounds  of  dry 
steam  is  a  fair  result;  8.25  is  a  good  result;  8.5  pounds 
very  good ;  and  9  pounds  about  the  best  attainable,  being 
rather  over  10,000  thermal  units,  which  corresponds  to  69 
per  cent  of  the  full  calorific  power  of  the  carbon,  and  is 
for  coal  consisting  of  83.33  Per  cent  of  carbon  a  high  re- 
sult. 

Q.  What  is  the  available  heat  of  combustion? 

The  available  heat  of  combustion  of  one  pound  of  any 
fuel  is  that  part  of  the  total  heat  of  combustion  which  is 
communicated  to  the  body,  to  heat  which  the  fuel  is 
burnt ;  the  water  in  a  steam  boiler,  for  example.  The 
theoretical  heat  of  any  fuel  is  easily  determined,  its  proxi- 
mate or  elementary  analysis  being  known;  but  the  actual 


214  COMBUSTION   OF   COAL. 

available  heat  can  be  determined  only  by  a  series  of  more 
or  less  elaborate  experiments  or  trials  in  actual  use. 

The  disposition  of  the  heat  generated  in  the  furnace  of 
a  steam  boiler  of  the  ordinary  horizontal  tubular  form  set 
in  brickwork,  and  provided  with  a  special  air-heating  ar- 
rangement which  lowered  the  temperature  of  the  flue  gases 
to  about  213°  F.,  and  raised  that  of  the  air  supplied  to  the 
furnace  about  300°  F.,  was  ascertained  by  Hoadley  to  be 
as  follows : 

Per  cent. 

Waste  in  flue  gases  including  evaporation  of  moisture  in 
coal  and  heating  vapor  in  air  when  these  losses  are  not 

separately  given 5.04 

Evaporating  moisture  in  coal 1.55 

Heating  vapor  in  air 1 8 

Imperfect  combustion 1.44 

Radiation  and  heat  not  otherwise  accounted  for 4.00 

Heating  and  evaporation  of  water 87.79 

The  high  efficiency  here  given  is  due  in  great  part  to 
the  recovery  of  heat  from  the  escaping  gases  and  the  pre- 
heating of  air  entering  the  furnace,  as  well  as  the  unusual 
care  and  skill  exercised  during  the  test.  These  results 
are  in  percentages  of  the  total  amount  of  heat  accounted 
for  in  heating  and  evaporating  water  in  the  boiler,  and 
are  fully  one-third  greater  than  obtains  in  good  ordinary 
practice. 


CHAPTER  X. 

STATIONARY  FURNACE  DETAILS. 

Q.  What  is  the  efficiency  of  a  furnace  ? 

The  efficiency  of  a  furnace  for  a  given  sort  of  fuel  is 
the  proportion  which  the  available  heat  bears  to  the  total 
heat  generated  in  the  furnace.  By  furnace  is  meant  not 
merely  the  chamber  in  which  the  combustion  takes  place, 
but  the  whole  apparatus  for  burning  the  fuel  and  transfer- 
ring heat  to  the  body  to  be  heated,  including  ash  pit,  com- 
bustion chamber,*  flues,  and  chimney. 

Q.  What  losses  occur  in  a  furnace  by  which  its  effi- 
ciency is  lowered? 

The  heat  generated  in  a  furnace  can  never  be  wholly 
utilized.  Heat,  like  water  or  steam,  must  flow  from  a 
higher  to  a  lower  level  in  order  to  become  available,  and 
in  any  such  transfer  there  are  always  losses,  among  which 
occur : 

Loss  due  to  radiation  of  heat  from  the  sides  of  the  fur- 
nace. 

Loss  occasioned  by  difference  of  temperature  between 
the  escaping  gases  and  that  of  the  atmosphere  necessary 
to  produce  natural  draught. 

Loss  by  the  waste  of  unburned  fuel  falling  through 
into  the  ash  pit. 

Loss  by  imperfect  combustion — that  is,  by  the  forma- 
tion of  carbonic  oxide  instead  of  carbonic-acid  gas. 


2l6 


COMBUSTION    OF    COAL. 


Loss  by  excess  of  air  passing  through  the  furnace,  doing 
no  useful  work. 

Q.  How  is  the  efficiency  of  a  steam   boiler   measured? 

In  steam  boilers 
the  efficiency  of  the 
furnace  is  measured 
by  the  pounds  of 
water  evaporated 
per  pound  of  coal 
burned  on  the  grate, 
under  known  con- 
ditions. The  effi- 
ciency is  expressed 
in  a  percentage  in- 
dicating how  nearly 
the  actual  perform- 
ance attains  to  the 
theoretical.  If  the 
latter  be  expressed 
by  100,  the  effici- 
ency will  always  be 
a  less  number. 

Suppose  a  coal  is 
known  to  contain 
13,100  heat  units 
by  calorimeter  test, 
the  equivalent  evap- 
oration from  and 
at  212°  F.  would 
be  13,100-4-  966  = 
13.56  pounds  of 
water  per  pound  of 


FURNACE    DIMENSIONS. 


217 


coal.     By  actual  test  9.25  pounds  of  water  are  evaporated 
per  pound  of  coal.      We  then  have : 

Efficiency    9'25  X  *°°  ==  68.22  per  cent. 
13-56 

The  loss  of  heat  in  this  case  amounts  to  31.78  per  cent 
of  the  total  heat  generated  in  the  furnace.     This  loss, 

PLAN  AT  A  B 


HALF  SECTION  AND  ELEVATION~OF  FRONT. 
FIG.  19. 

which  is  largely  unavoidable,  may  be  accounted  for  as  on 
page  2 is- 

Good  boilers,  properly  set  and  well  managed,  will  average 
nearly  the  same  efficiency,  approximating  65  per  cent. 

Q.  What    are   the   ordinary   furnace    dimensions   for   a 
horizontal  tubular  boiler  ? 

There  are  no  standard  dimensions  for  boiler  settings  or 


218 


COMBUSTION    OF   COAL. 


FURNACE    DIMENSIONS. 


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220  COMBUSTION   OF   COAL. 

furnaces ;  the  practice  varies  as  between  East  and  West, 
and  between  anthracite  and  bituminous  fuels.  A  very 
good  design  is  shown  in  Fig.  20  in  sectional  elevation. 
This  design  is  by  the  Bigelow  Company,  New  Haven, 
Conn.  A  plan  is  shown  in  Fig.  18  and  a  half  front  eleva- 
tion and  half  section  is  shown  in  Fig.  19. 

The  bottom  of  the  front  should  set  up  5  inches  (2 
bricks)  above  the  floor  level.  Front  edge  of  moulding  on 
bottom  of  front  should  set  back  2  inches  from  front  edge 
of  brick  work.  Both  of  these  details  are  shown  in  Fig. 
20.  All  measurements  given  in  Table  26  are  based  on 


FIG.  21. 

the  front  being  set  as  stated  above.  Ash  pits  under  the 
grates  should  slope  down  from  bottom  of  ash  door  to  floor 
level.  The  front  wing  brackets  on  the  boiler  should  rest 
directly  on  the  wall  plates  so  that  all  the  expansion  will 
go  to  the  rear,  provision  being  made  for  this  longitudinal 
movement  by  rollers  placed  between  the  rear  wing  brack- 
ets and  the  wall  plate  underneath. 

The  inside  walls  in  this  design  taper,  beginning  at  the 
top  of  the  grates  and  extending  to  a  line  4  inches  under 
the  bracket,  giving  a  space  of  2  inches  between  the  side 
of  boiler  and  inside  of  wall,  as  shown  at  Z  in  Fig.  19. 
The  inside  wall  should  close  in  to  the  boiler  on  a  line  2^ 
inches  (i  brick)  under  the  brackets.  The  outside  and  in- 
side walls  have  a  2- inch  air  space  between  them.  Head- 
ers should  be  run  from  wall  to  wall,  say,  every  1 8  inches, 
but  not  tied  together.  Fire  brick  in  the  furnace  should 
be  laid  with  a  course  of  headers  every  five  or  six  courses, 


KENT'S    BOILER    SETTING.  221 

so  that  portions  of  the  wall  can  be  easily  taken  out  and 
repaired.  Boilers  should  be  covered  on  top  with  some 
non-conducting  material ;  if  with  a  brick  arch,  an  air 
space  of  2  inches  should  be  left  between  the  boiler  and 
the  brick  work.  The  arch  tee  bars  for  back  connection 
should  be  lined  with  fire  brick  laid  endwise  before  the 
bars  are  placed  in  position,  as  in  Fig.  21. 

Q.  What  are  the  details  of  construction  of  Kent's  fur- 
nace for  steam  boilers  ? 

This  design  of  furnace,  shown  in  longitudinal  sectional 
elevation  in  Fig.  22,  is  intended  especially  for  furnaces 
which  use  bituminous  coal,  lignite,  peat,  tan  bark,  or  other 
fuel  which  contains  large  quantities  of  tarry  or  gaseous 
matter,  and  which  in  burning  distils  a  large  amount  of 
combustible  gases. 

The  fire  chamber,  built  of  brick,  extends  out  in  front  of 
the  boiler ;  in  it  the  fuel  is  burned,  either  on  the  ordinary 
grate  bars,  or  by  any  one  of  the  numerous  stokers  now  in 
the  market.  A  bridge  wall  is  provided  at  the  end  of  the 
grates,  over  which  the  gaseous  products  of  combustion  pass 
on  their  way  to  the  heating  surfaces  of  the  boiler.  Two 
wing  walls  are  built  parallel  to  and  at  some  distance  in  the 
rear  of  the  bridge  wall,  as  shown  in  Fig.  23.  A  gas-mix- 
ing chamber  is  thus  formed  between  the  bridge  and  wing 
walls.  The  combustion  chamber  is  the  next  into  which 
the  gases  travel  from  the  passage  between  the  wing  walls. 
In  this  chamber  are  several  piers  of  fire  brick  projecting 
in  front  of  the  wall  at  the  rear  of  the  combustion  chamber. 
The  remaining  details  of  the  setting  are  those  of  the  Bab- 
cock  and  Wilcox  boiler,  and  readily  understood. 

In  the  operation  of  this  furnace,  with  ordinary  grates 
and  with  bituminous  coal  or  other  gaseous  fuel,  the  alter- 


222 


COMBUSTION   OF   COAL. 


KENT'S    BOILER    SETTING. 


223 


nate  method  of  feeding  coal  is  preferred — that  is,  the  fresh 
coal  is  spread  alternately  on  the  right  and  left  sides  of 
the  grate,  an  interval  of  some  minutes  of  time  elapsing 
between  the  feeding 
on  the  right  and  on 
the  left  side.  Immedi- 
ately after  fresh  coal 
is  put  on  one  side  of 
the  furnace  dense 
smoky  gases  arise 
from  it,  which  in  the 
ordinary  boiler  setting 
would  pass  out  of  the 
chimney  unburned, 
since  in  the  ordinary 
setting  there  is  no 
means  provided  for 
mixing  with  them  an 
abundant  supply  of 
highly  heated  air;  but 
in  this  furnace  such 
air  is  supplied  through 
the  bed  of  partially 
burned  and  very  hot 
coal  and  coke  on  the 
other  side  of  the 
grate.  The  two  cur- 
re  n  t  s,  one  of  cool 
smoky  gas  arising 
from  the  fresh  coal  on 
one  side  of  the  grate 
and  the  other  of  clear 
and  very  hot  gas  con- 


224  COMBUSTION   OF   COAL. 

taining  a  large  excess  of  air,  pass  together  over  the  bridge 
wall  and  are  compelled  by  the  wing  walls  to  change 
their  direction  and  to  mix  together  in  the  gas-mixing 
chamber  and  in  the  contracted  vertical  passage  between 
the  wing  walls.  The  combustion  of  the  unburned  gas 
is  further  rendered  more  certain  and  complete  by  passing 
through  the  large  combustion  chamber,  whose  walls,  to- 
gether with  the  fire-brick  piers,  are  in  a  highly  heated 
state  and  perform  the  functions  of  a  regenerative  furnace 
— that  is,  they  absorb  heat  from  the  burned  gases  at  such 
times  as  they  are  most  intensely  heated,  and  radiate  or 
give  up  heat  at  such  times  as  the  gases  are  not  so  hot,  as 
during  the  first  minute  after  feeding  fresh  coal,  when 
there  is  a  great  excess  of  freshly  distilled  and  rather  cool 
gases. 

By  this  means  complete  combustion  of  the  smoky  gases 
is  secured  in  the  combustion  chamber  when  reasonable 
care  is  used  by  the  fireman,  and  the  resulting  thoroughly 
burned  products  of  combustion  are  then  in  the  right  con- 
dition to  be  allowed  to  traverse  the  gas  passages  through 
the  tubes  and  give  up  their  heat  to  the  boiler. 

Q.  What  are  the  details  of  construction  of  the  O'Brien 
and  Pickles  down-draft  furnace  ? 

A  longitudinal  section  of  this  furnace  is  shown  in  Fig. 
24.  It  consists,  in  common  with  down-draft  furnaces 
generally,  of  two  grates,  an  upper  and  a  lower  one ;  the 
raw  fuel  being  fed  to  the  upper  grate  where  it  burns, 
the  draft  passing  in  through  openings  in  the  upper  fire 
door,  down  through  the  fuel  on  the  upper  grate,  and  under 
the  inner  manifold  shown  immediately  over  the  bridge 
wall.  This  manifold  has  communication  with  tne  boiler 
by  the  elbow  and  connections  clearly  shown.  On  top  of 


DOWN-DRAFT    FURNACE. 


225 


the  inner  manifold  is  a  fire-brick  partition  closing  the 
space  between  it  and  the  boiler,  and  compelling  the 
draft  to  flow  downward. 

The  front  manifold  is  placed  directly  under  the  front 
end  of  the  boiler,  and  between  it  and  the  inner  manifold 


FIG.  24. 

are  tubular  grates,  through  which  water  circulates  from 
one  manifold  to  the  other. 

Any  fuel  that  falls  through  the  upper  grate  is  caught 
by  the  lower  one,  upon  which  it  burns,  the  draft  pass 
ing  in  through  the  lower  or  ash-pit  door,  up  through 
the  grate  and  beneath  the  inner  manifold.  The  grate 
bars  for  the  lower  series  are  of  the  ordinary  pattern, 
the  spaces  being  much  finer  than  obtain  in  the  upper 
series. 


226 


COMBUSTION   OF   COAL. 


Q.  What  is  the  construction  and  operation  of  the  Bab- 
cock  and  Wilcox  automatic  stoker? 

This  is  an  endless-chain  grate  stoker.  It  is  shown  in 
perspective  in  Fig.  25,  wholly  withdrawn  from  the  furnace. 
The  grate  is  made  up  of  a  series  of  short  cast-iron  bars 
linked  together  and  engaging  sprockets  at  the  front  and 
rear,  by  the  movement  of  which  the  upper  portion  of  the 
grate  is  carried  constantly  forward.  The  coal  is  fed 


FIG.  25. 

through  a  hopper  of  the  full  width  of  the  grate,  and  the 
depth  of  the  layer  is  regulated  by  a  door  which  can  be 
lifted  or  lowered.  The  coal  is  ignited  near  the  front  and 
is  carried  slowly  backward,  the  speed  of  the  grate  being 
adjusted  so  that  the  time  of  travel  is  sufficient  for  the 
complete  combustion  of  the  fuel,  the  ash  and  refuse  being 
carried  over  at  the  back  end  and  falling  into  the  ash  pit. 
A  fire-brick  arch  at  the  front  end  of  the  furnace  facilitates 
the  coking  of  the  fresh  fuel  as  it  enters,  and  the  combus- 


RONEY'S    MECHANICAL    STOKER. 


227 


tion  of  the  volatile  gases  evolved.  The  apparatus  as  a 
whole  is  mounted  on  wheels  running  on  rails  placed  on  the 
sides  of  the  ash  pit,  and  can  be  drawn  out  clear  of  the 
boiler  for  inspection  or  repairs,  or  to  give  room  when  nec- 
essary to  replace  furnace  linings. 

Q.  What  is  the  construction  and  operation  of  the  Roney 
mechanical  stoker  ? 

This  stoker  is  shown  in  connection  with  a  horizontal 
tubular  boiler  setting  in  Fig.  26  and  in  detail  in  Fig.  27. 


FIG.  26. 

It  consists  of  a  hopper  for  receiving  the  coal,  a  set  of 
rocking  stepped  grate  bars,  inclined  at  an  angle  of  37° 
from  the  horizontal,  and  a  dumping  grate  at  the  bottom  of 
the  incline  for  receiving  and  discharging  the  ash  and 
clinker. 

The  coal  is  fed  on  to  the  inclined  grates  from  the  hop- 
per by  a  reciprocating  pusher,  which  is  actuated  by  the 
agitator  and  agitator  sector.  The  grate  bars  rock  through 


228 


COMBUSTION   OF   COAL. 


an  arc  of  30°,  assuming  alternately  the  stepped  and  the 
inclined  position.  They  receive  their  motion  from  the 
rocker  bar  and  connecting  rod,  and  these,  with  the  pusher, 
are  actuated  by  the  agitator,  which  receives  its  motion 
through  the  eccentric  from  a  shaft  attached  to  the  stoker 
front  under  the  hopper.  The  range  of  motion  of  the 


COKING-ARCrt 


AGITATOR 
FEED-WHEEL1 


AGITATOR  SECTOR 


6HEATH-NUT 


FIG.  27. 

pusher  is  regulated  by  the  feed  wheel  from  no  stroke  to 
full  stroke,  and  the  amount  of  coal  pushed  into  the  fur- 
nace adjusted,  according  to  the  demand  for  steam.  The 
motion  of  the  grate  bars  is  similarly  regulated  and  con- 
trolled by  the  position  of  the  sheath-nut  and  lock-nuts  on 
the  connecting  rod.  Each  grate  bar  is  composed  of  two 
p-erts :  a  vertical  web  provided  with  trunnions  at  each 
end,  which  rest  in  seats  in  the  side  bearers,  and  a  fuel 


WILKINSON'S  MECHANICAL  STOKER. 


229 


plate  ribbed  on  its  under  side,  which  bolts  to  the  web. 
These  fuel  plates  carry  the  bed  of  burning  coal,  and  be- 
ing wearing  parts  are  made  detachable  to  facilitate  repairs. 
The  webs  are  perforated  with  longitudinal  slots,  so  placed 
that  the  condition  of  the  fire  can  be  seen  at  all  times  with- 
out opening  the  doors ;  and  free  access  had  to  all  parts  of 
the  grate  to  assist,  when  necessary,  the  removal  of  clinker. 
For  bituminous  coal  a  coking  arch  of  fire  brick  is  sprung 
across  the  furnace,  covering  the  upper  part  of  the  grate 
and  forming  a  reverberatory  furnace  and  gas  producer, 
whose  action  is  to  coke  the  fresh  fuel  as  it  enters  and  re- 
lease its  gases.  These,  mingling  with  the  heated  air  sup- 
plied in  small  streams  through  the  perforated  tile  above 
the  dead  plate,  are  quickly  burned  in  the  large  combustion 
chamber  above  the  bed  of  incandescent  coke  on  the  lower 
part  of  the  grate. 

Q.  What   is   the    construction    of   the   Wilkinson   auto- 
matic stoker  ? 

Three  views  are  shown  of  this  stoker,  Fig.  28  being  a 
front  view,  Fig.  29  the  furnace  view,  Fig.  30  a  sectional 


FIG.  28. 


230 


COMBUSTION   OF   COAL. 


elevation,  to  which  has  been  added  a  rtsumt  of  the  process 
of  combustion.     The  grate  bars  are  hollow,  as  shown  in 


FIG.  29. 


Fig.  30.     They  are  placed  side  by  side  and  inclined  toward 
the  bottom  of  the  furnace  at  an  angle  suited  to  the  repose 


AIR 

8TEAM      JX 
OXYGEN     >"•• 
HYDROGEN 
ALL  BURN  AS 


AIR        ) 
OXYGEN    J- 

NITROGEN' 

r  V*  COMBUSTIBLE 


COMPOSITION  OF  WATER  GAS 
CARBONIC  OXIDE.HYDROGEN 


FIG.  30. 


AYRES  AND  RANGER  STOKER.         231 

of  the  fuel,  and  they  are  so  constructed  as  to  admit  of  suffi- 
cient air  through  the  fire  to  the  combustion  chamber. 
The  lower  ends  of  these  grates  slide  upon  and  are  sup- 
ported by  a  cast-iron  box.  This  box  has  finger  grates, 
about  1 5  inches  long,  secured  to  its  rear  face.  Through- 
out the  inclined  length  of  each  grate  is  cast  a  succession 
of  steps.  Through  the  rise  of  each  step  a  vent  of  about 
y±  X  3  inches  is  provided  to  admit  air  through  the  fire  to 
the  combustion  chamber.  A  continuous  back  and  forth 
motion  is  given  the  grates  for  the  purpose  of  maintaining 
a  uniform  thickness  of  fire  by  a  gradual  descent  of  the 
fuel  from  the  top  to  the  bottom  of  the  grate,  depositing 
the  clinker  and  ash  on  the  stationary  grate  shown  project- 
ing from  the  cast-iron  box  forming  the  lower  bearing  bar 
at  the  ash  pit.  The  accumulated  ash  is  pushed  off  this 
stationary  grate  into  the  ash  pit  by  the  reciprocating  mo- 
tion of  the  bars,  to  be  removed  in  the  usual  manner. 

The  blast  is  saturated  steam  through  a  nozzle  of  y^-inch 
diameter,  giving  an  induced  current  of  air  controlled  by  a 
regulating  valve. 

The  motor  for  operating  the  grates  may  be  either  hy- 
draulic or  steam  attached  to  each  stoker,  or  a  small  engine 
may  be  employed  for  operating  several  stokers. 

Q.  What  are  the  details  of  construction  of  the  Ayres 
and  Ranger  mechanical  stoker  ? 

This  stoker  is  shown  in  connection  with  the  flue  of  an 
internally  fired  boiler  in  Fig.  31;  a  front  elevation  is 
shown  in  Fig.  32.  This  stoker  belongs  to  the  class  known 
as  coking  stokers.  The  coal  is  fed  into  the  hopper  shown 
at  the  front  end  of  boiler;  at  the  bottom  of  this  hopper  is 
a  series  of  propeller- shaped  blades  joined  to  and  radiating 
from  a  sleeve  mounted  on  a  shaft,  which  is  caused  to  ro- 


232 


COMBUSTION   OF   COAL. 


tate  intermittently  at  any  desired  speed ;  and  by  these  the 
coal  is  propelled  through  an  opening  in  the  furnace,  on  to 
an  inclined  guide  plate,  and  from  this  upon  a  perforated 
dead  plate  below,  and  by  this  means  the  coal  is  equally 
distributed  across  the  front  of  the  furnace,  forming  a  bank 
or  ridge  of  coal  to  be  there  coked,  and  to  be  then  carried 
by  moving  fire  bars  to  the  back  of  the  furnace.  The  fire 
bars  are  so  arranged  that  every  other  one  is  stationary ; 
the  moving  bars  are  actuated  by  a  cam  or  other  device  by 
which  an  up-and-down  vertical  movement  may  be  imparted 
to  the  front  end  of  the  bars.  This  cam  in  continuing  its 
movement  then  engages  the  end  of  the  moving  bar  and 


FIG.  31. 

pushes  it  in  the  direction  of  the  arrow,  Fig.  31.  The  end 
of  the  bar  being  tapered  rides  up  on  the  roller  at  the  rear 
of  the  furnace,  and  thus  raises  that  end  of  the  bar.  By 
the  return  motion  of  the  cam  the  bar  is  brought  back  to 
its  normal  position.  This  continual  motion  of  the  mova- 


THE    MURPHY    FURNACE. 


233 


ble  bars  carries  the  fuel  gradually  from  the  front  to  the 
rear  of  the  furnace.  It  also  serves  to  break  up  the  clink- 
ers, clear  the  air  spaces,  ultimately  depositing  the  ex- 
hausted portion  of  the  fuel 
into  the  ash  or  clinker  pit  at 
the  end  of  the  bars  in  the 
usual  way. 

Q.  What  are  the  principal 
details  of  the  Murphy  furnace  ? 

A  cross- sectional  elevation 
of  the  Murphy  self-feeding 
furnace  is  shown  in  Fig.  33. 
The  grate  bars  are  arranged 
on  opposite  sides  of  the  fur- 
nace chamber  and  incline 
downwardly  toward  the  cen- 
tre, the  fuel  being  introduced 
at  the  top  and  fed  down  tow- 
ard the  middle,  in  which  there 

is  a  device  for  mechanically  removing  the  clinkers.  A  fire- 
brick arch  spans  the  combustion  chamber.  A  coal  maga- 
zine is  located  at  each  side  of  the  furnace  and  is  provided 
with  discharge  openings  and  coal  pushers.  The  latter 
have  a  reciprocating  motion  imparted  to  each  by  a  rock 
shaft,  rack,  and  pinion. 

The  inclined  grate  surface  is  composed  of  stationary  and 
movable  grate  bars,  alternately  placed.  The  upper  ends 
of  the  stationary  grate  bars  abut  against  a  compensating 
plate,  which  permits  the  bars  to  expand  readily  with  the 
heat.  The  movable  grate  bars  are  connected  to  vibrating 
levers,  from  whence  they  derive  their  motion.  In  connec- 
tion with  this  motion  the  movement  of  the  rock  shaft  im- 


FlG. 


234 


COMBUSTION   OF   COAL. 


parts  motion  to  the  coal  pushers  in  a  manner  to  feed  the 
coal  just  in  proportion  to  the  requirements  of  the  furnace. 
The  crushing  and  removal  of  the  ashes  and  clinkers  is 
effected  by  a  clinker  bar  at  the  bottom  of  the  grates.  The 
clinker  bar  is  provided  on  the  outside  with  teeth  which 


FIG.  33. 

extend  spirally  around  the  bar,  and  the  approximate  inner 
edges  of  the  grate  bearers  are  provided  with  similar  teeth 
to  aid  in  crushing  the  clinkers  when  the  clinker  bar  is 
rocked. 

The  furnace  is  especially  adapted  for  the  use  of  small 
sized  bituminous  coal  and  slack,  which  is  put  into  maga- 
zines at  the  side  of  the  combustion  chamber.  Air  is  ad- 


THE   AMERICAN    STOKER.  235 

mitted  through  a  register  at  the  front,  passes  through  flues 
up  over  the  arch,  and  there  takes  up  heat  from  the  front, 
arch,  and  arch  plate,  passing  down  through  the  small 
openings  in  the  arch  plate  to  the  coking  fuel.  It  is 
claimed  that  this  furnace  has  a  coking  capacity  sufficient 
to  feed  50  pounds  of  coal  per  square  foot  of  grate  per 
hour. 

On  the  side  of  a  battery  of  boilers  is  placed  an  engine 
with  proper  gearing  for  operating  a  reciprocating  bar  across 
the  outside  of  the  entire  front,  and  to  which  all  the  work 
ing  parts  are  attached  by  links. 

Q.  What  is  the  construction  and  operation  of  the  Ameri- 
can stoker  ? 

This  stoker  belongs  to  the  not  very  numerous  class  of 
underfeeding  devices.  The  illustration  Fig.  34  shows  it 
in  longitudinal  section,  and  Fig.  35  in  cross-sectional  ele- 
vation. The  stoker  consists  of  a  coal  hopper,  a  conveyor 
pipe,  a  screw  conveyor,  a  coal  magazine  under  the  furnace 
level,  a  wind  box,  and  a  reciprocating  piston  motor  with  a 
ratchet-feed  attachment  for  operating  the  screw  conveyor. 
The  rate  of  feeding  coal  is  controlled  by  the  speed  of  the 
motor,  this  being  effected  by  the  simple  means  of  throt- 
tling the  steam  in  the  supply  pipe  to  the  motor. 

The  coal  is  fed  into  the  hopper  either  by  hand  or  by 
overhead  conveyor  mechanism.  It  descends  of  course  into 
the  receptacle  below,  in  which  is  contained  the  screw 
which  conveys  it  into  the  magazine  in  the  furnace  proper. 
The  continuous  supply  causes  the  coal  thus  fed  to  over- 
flow on  both  sides,  and  spread  upon  the  side  grates,  shown 
in  Fig.  35.  As  the  fresh  coal  approaches  the  fire  in  its 
upward  course  it  is  slowly  roasted  or  coked.  The  gases 
released  from  the  coal  mingle  with  the  incoming  air 


236 


COMBUSTION   OF   COAL. 


through  the  tuyeres  and  are  burned,  leaving  only  the  in- 
candescent coke  for  delivery  on  the  side  grates. 

The  non-combustible  ash  and  clinker  is  deposited  on  the 
side  grates  by  the  constant  upward  feeding  of  the  coal. 
One  open  grate  against  each  wall  admits  air  mixed  with 


FIG. 


34- 


the  exhaust  steam  from  the  motor,  which  serves  to  prevent 
the  clinker  sticking  to  the  walls.  To  clean,  a  slice  bar  is 
run  along  over  the  grate,  the  clinker  raised  and  drawn  out 
with  a  hook.  The  central  part  of  the  fire  is  never  dis- 
turbed, as  the  constant  feeding  does  all  the  stoking  neces- 
sary. The  fire  doors  are  never  opened  except  when  clean- 
ing. 

This  stoker  requires  a  blower  for  supplying  the  air  nee- 


THE   JONES    UNDERFEED    STOKER. 


237 


essary  for  combustion,  the  air  pressure  varying  from  I  to 
i  Y?  ounces,  depending  upon  the  quality  of  fuel  and  depth 
of  fire.  The  latter  is  ordinarily  from  14  to  18  inches 
thick  above  the  tuyere  blocks. 


Q.  What  is  the  construction  and  operation  of  the  Jones 
underfeed  mechanical  stoker  ? 

This  stoker  is  shown  in  sectional  elevation  in  Fig.  36, 
and  in  cross  section  on  the  line  A-B  in  Fig.  37.  The 
stoker  consists  of  a  steam  cylinder  or  ram,  with  a  coal  hop- 
per, outside  of  the  furnace  proper ;  a  retort  or  fuel  maga- 
zine inside  the  furnace,  on  the  sides  of  which  are  placed 
tuyere  blocks  for  the  admission  of  air.  The  retort  also 
contains  at  its  lowest  point  an  auxiliary  ram  or  pusher 


238  COMBUSTION   OF   COAL. 

which  causes  the  coal   to   be    evenly   distributed.      This 
pusher  is  in  a  position  where  the  fire  never  reaches. 

The  retort  is  first  filled  with  coal,  on  a  level  or  a  little 
above  the  tuyere  blocks.  The  fire  is  then  started  along 
each  side  of  the  retort,  the  air  chambers  reaching  to  the 
tuyere  blocks  being  opened.  As  soon  as  the  fire  is  well 
under  way,  the  air  chamber  opening  is  closed  and  the 
blower  started ;  the  fire  will  then  be  built  up  very  rapidly. 


ONE  BLOCK  IN  PLACE 


FIG.  36. 

Coal  being  in  the  hopper,  and  the  ram  plunger  on  its 
forward  stroke,  when  more  coal  is  needed  the  plunger  is 
shifted  back  by  moving  the  lever,  coal  then  falls  in  front 
of  the  plunger,  steam  is  admitted  to  the  cylinder  and  the 
plunger  forced  forward,  pushing  the  coal  into  the  retort. 
Coal  is  pushed  into  the  retort  as  needed  to  replenish  that 
consumed. 

Air  at  low  pressure  is  admitted  into  the  air  chamber 
and  through  the  tuyere  blocks,  over  the  top  of  the  green 
fuel  in  the  retort,  but  under  and  through  the  burning  fuel ; 
the  result  is  that  the  heat  from  the  burning  fuel  over  the 
retort  slowly  liberates  the  gas  from  the  green  fuel,  this 


THE    Mf CLAVE    GRATE. 


239 


gas  being  thoroughly  mixed  with  the  incoming  air  before 
it  passes  through  the  burning  fuel,  resulting  in  a  bright, 
clear  fire,  free  from  smoke.  The  retort  being  air  tight 
from  below,  and  the  fuel  being  in  a  compact  mass,  the 
air  moves  upward  and  combustion  takes  place  only  above 
the  air  slots.  The  retort  is  thus  kept  cool  and  not  subject 
to  the  action  of  the  fire.  The  incoming  fresh  fuel  from 
the  retort  forces  the  resulting  ash  and  clinker  over  the  top 
of  the  tuyere  blocks  on  to  the  side  plates,  from  which  they 


CROSS  SECTION 
LINE  A-B 


FIG.  37. 


can   be  easily  removed  at   any  time  without   interfering 
with  the  fire  in  the  centre  of  the  furnace. 

Q.  What  is  the  construction  of  the  McClave  grate  ? 

This  grate  is  shown  in  Fig.  38,  which  represents  the 
shaking  movement,  and  Fig.  39,  which  represents  the  cut- 
off movement.  The  shaking  movement  is  adapted  for 
breaking  up  a  soft  coal  fire  when  it  cakes,  or  to  remove 
fine  ashes  from  a  hard  coal  fire  when  there  is  but  little  or 
no  clinker  formed.  In  this  movement  there  is  no  increase 
of  openings  during  the  operation,  the  bars  keeping  equi- 
distant from  each  other  in  their  travel  from  the  normal 
position  downward  and  return. 


240 


COMBUSTION   OF   COAL. 


The  cut-off  movement  is  used  principally  for  fine  an- 
thracite fuel,  such  as  culm,  buckwheat,  and  pea  coal. 
Small  anthracite  fuels  should  not  be  shaken  or  stirred  up 


FIG.  38. 


in  any  manner  until  it  becomes  necessary  to  give  the  fire  a 
thorough  cleaning.  It  should  then  be  cleaned  as  quickly 
as  possible.  For  all  free-burning  varieties  of  coal  that  do 
not  produce  large  slabs  of  clinkers  this  movement  removes 


^.^^^_^— ^-_.^.^^^__^;,..___: 


FIG.  39. 


the  clinkers  and  ashes  from  the  bottom  of  the  fire  quickly 
and  thoroughly  without   opening  the  fire  door. 


THE   FISHER   BAGASSE   FURNACE.  24! 

Single  lever  connections  are  used  for  grates  less  than  5 
feet  in  length,  and  the  width  of  the  grates  is  generally 
made  in  two  or  more  rows.  To  clean  a  fire  when  the  fuel 
clinkers  badly,  the  unconsumed  fuel  of  one  row  can  be 
shoved  over  on  the  other  row,  and  with  the  full  cut-off 
movement  the  clinkers  and  ashes  can  be  cut  down  into  the 
ash  pit ;  then  shove  all  the  unconsumed  fuel  on  to  the 
clean  row  of  bars  and  cut  the  clinkers  down  the  same  as 
before ;  then  redistribute  the  unconsumed  fuel  over  the 
whole  grate. 

Q.  What  are  the  details  of  construction  of  the  Fisher 
apparatus  for  feeding  bagasse  to  steam  boiler  furnaces? 

The  feeding  of  bagasse  to  a  boiler  furnace  by  Fisher's 
method  is  shown  in  Fig.  40,  which  consists  of  an  inclined 
chute  down  which  the  bagasse  is  fed.  At  the  lower  end 
and  near  the  furnace  front  is  a  roller  having  radial  blades, 
which  roller  is  driven  by  any  suitable  mechanism.  Be- 
tween this  roller  and  the  furnace  front  is  a  perforated 
steam  or  air-blast  pipe  extending  across  the  chute.  There 
is  attached  to  the  furnace  front  a  pivoted  door  extending 
over  both  the  perforated  blast  pipe  and  bladed  roller.  A 
second  door  is  hinged  to  the  one  just  referred  to  and  is 
adapted  for  closing  the  chute.  These  doors  fit  in  between 
the  sides  of  trie  chute,  and  thus  being  practically  air  tight 
prevent  the  escape  of  any  sparks  which  might  otherwise 
fly  out  from  the  mouth  of  the  furnace. 

The  bagasse  after  being  discharged  upon  the  chute 
slides  down  to  the  bladed  roller,  which  is  constantly  rotat- 
ing and  which  feeds  the  bagasse  along  over  the  perforated 
pipe,  from  which  latter  let  it  be  supposed  there  is  escaping 
a  blast  of  air  or  steam  under  pressure.  As  the  material 
16 


242 


COMBUSTION    OF   COAL. 


passes  over  this  perforated  pipe,  the  blast  of  air  or  steam 
escaping  therefrom  lifts  the  material  and  scatters  it  in  all  di- 


FlG.  40. 

rections  over  the  furnace  grate,  thus  rendering  it  impossi- 
ble for  any  large  mass  of  the  material  to  fall  in  one  spot 
and  there  retard  combustion.  Besides  the  function  of 


HEGGEM'S    FIRE    KOX. 


243 


scattering  the  finely  divided  particles  of  the  fuel  over  the 

grate  bars  the  blast  of  steam   or  air  will  create  a  better 

draft  in  the  furnace,  and  thus  materially  assist  combus- 
tion. 

Q.  What  are  the   details    of   construction   of   Heggem's 
boiler  for  burning  straw  ? 

This  boiler  is  particularly  adapted  for  agricultural  use, 
and  is  of  the  usual  portable  type;  but  the  object  of  the 


^ 

o      o      o      o      o      o      <5 


FIG.  4 


present  design  is  that  the  boiler  shall  be  capable  of  burn- 
ing alternately  either  straw  or  solid  fuel,  as  may  be  desired, 


244 


COMBUSTION   OF   COAL. 


the  fire  box  being  provided  with  a  draft  apparatus  that  may 
be  made  applicable  in  each  case  for  the  particular  fuel 
burned.  This  boiler  is  shown  in  sectional  elevation  in 
Fig.  41,  and  shows  the  arrangement  of  dampers  when 
using  straw  as  fuel,  in  which  case  a  funnel  is  fitted  to  the 
usual  fire-door  opening;  this  funnel  being  provided  with  a 


hinged  door,  the  free  end  of  which  is  adapted  to  rest  con- 
tinually against  the  straw  as  it  is  forced  into  the  fire  box. 
The  damper  under  the  barrel  of  the  boiler  being  raised, 
as  shown  in  the  engraving,  causes  the  draft  to  flow  into 
the  fire  box,  as  indicated  by  the  arrows,  causing  the 


ALLEN    AND    TTBBITTS    FURNACE.  24$ 

straw  to  burn  at  the  ends,  as  it  is  forced  in  through  the 
funnel. 

Fig.  42  shows  the  same  boiler  with  the  straw-feeding 
funnel  removed,  the  regular  fire  door  in  place,  the  closing 
of  the  damper  under  the  barrel  of  the  boiler  and  the  open- 
ing of  the  damper  or  ash-pit  door  under  the  fire  door,  and 
the  use  of  coal  as  fuel. 

Q.  What  are  the  details  of  construction  of  the  Allen 
and  Tibbitts  apparatus  for  feeding  comminuted  fuel  to 
furnaces  ? 

A  vertical  section  of  a  steam  boiler  furnace  showing  the 
apparatus  in  operation  is  given  in  Fig.  43.  The  operation 
consists  in  spraying  the  fine  particles  of  fuel  into  the  fur- 
nace by  means  of  rapidly  revolving  distributing  rollers. 
On  the  circumference  of  the  rollers  are  provided  ribs, 
which  are  fixed  in  diagonal  lines  from  the  middle  to  the 
ends  of  the  rollers.  These  rollers  are  given  rapid  revolv- 
ing motion,  and  are  designed  for  throwing  the  fine  fuel 
into  the  furnace  by  their  centrifugal  force.  There  is  a 
rotary  vertical  spiral  conveyor  enclosed  in  a  pipe  and 
stepped  in  the  bottom  of  a  coal  supply  pit  in  the  floor  in 
front  of  the  furnace.  At  the  top  of^  this  pipe  are  branch 
pipes  leading  from  the  head  of  the  vertical  pipe  and  ex- 
tending over  and  communicating  with  the  interior  of  the 
boxes  containing  the  revolving  rollers,  by  which  the  fuel 
is  delivered  into  the  furnace  in  a  shower  or  spray  in  the 
upper  part  of  the  combustion  chamber,  so  that  the  parti- 
cles will  catch  fire  in  transit  and  be  consumed  or  partly 
consumed  before  falling  upon  the  fire  floor,  the  draft 
being  through  the  grated  doors,  thus  avoiding  the  opening 
of  the  doors  for  feeding  purposes.  In  instances  when  the 
fire  dust  is  used  no  grate  bars  need  be  employed  in  the 


246 


COMBUSTION    OF   COAL. 


floor;  but  as  a  general  rule,  when  the  coarser  grades  of 
fuel  are  used,  grate  bars  should  be  used  for  providing  a 
draft  upward  into  the  fire. 


FIG.  43- 


THE    ROGERS    FURNACE    FEEDER.  247 

Q.  What  are  the  details  of  construction  of  the  Rogers 
apparatus  for  feeding  fine  fuel  ? 

This  apparatus  is  designed  for  feeding  fine  fuels,  such 
as  rice  hulls,  cotton  hulls,  sawdust,  etc.  A  cross -section- 
al elevation  of  a  boiler  furnace  with  the  apparatus  also  in 
section  is  shown  in  Fig.  44.  This  apparatus  consists  of  a 
hopper  placed  at  the  side  of  the  furnace  and  near  the  front 
end  of  the  boiler,  a  steam  blast  pipe,  and  a  nozzle  for  dis- 
tributing the  fuel  over  the  grate.  This  nozzle  is  made  with 
one  straight  side  placed  parallel  to  the  boiler  front ;  the 
opposite  or  rear  side  is  formed  obliquely  toward  the  bridge 
wall.  A  sliding  gate  opens  or  closes  communication  be- 
tween the  hopper  and  the  furnace.  For  the  purpose  of 
superheating  the  steam  used  in  the  blast  nozzle,  its  supply 
pipe  passes  along  the  side  of  the  boiler,  to  the  rear  and 
return,  thence  into  the  discharging  pipe. 

The  fire  may  be  started  in  the  furnace  in  any  approved 
way  and  with  any  desired  fuel.  The  sliding  gate  is  then 
opened,  as  is  also  the  steam  cock,  whereupon  the  hulls  or 
sawdust  resting  in  the  hopper  and  chute  are  caused  by  the 
suction  of  the  steam  blasts  to  discharge  through  the  nozzle 
into  the  furnace,  over  the  fire  bed  in  thin  sheets,  in  the 
manner  illustrated  in  the  engraving.  Should  the  supply 
become  excessive,  the  sliding  gate  and  steam  cocks  are 
closed.  When  the  gate  is  closed,  no  back  blast  through 
the  hopper  can  occur,  and  danger  from  fire  in  the  hopper 
or  chute  will  be  prevented  at  such  times  as  the  feeder 
may  not  be  in  use. 


248 


COMBUSTION    OF    COAL. 


CHAPTER  XL 

LOCOMOTIVE   FURNACE   DETAILS. 

Q.  What  are  the  ordinary  limitations  of  a  locomotive 
fire  box  ? 

The  width  of  the  fire  box  is  limited  to  the  distance  be- 
tween the  frames  inside  of  the  driving  wheels ;  the  neces- 
sary outside  clearance ;  and  the  thickness  of  the  two  water 
legs  from  out  to  out.  The  inside  width  will  be  about 
41%  inches.  The  length  of  the  fire  box  will  depend 
somewhat  upon  the  size  and  type  of  the  boiler  and  the 
arrangement  of  the  axles  for  the  driving  wheels ;  in  gen- 
eral, this  length  is  limited  to  about  10  feet. 

Q.  What  are  the  objections  to  a  long  fire  box  ? 

Mainly  the  inconvenience  occasioned  in  firing,  as  the 
proper  distribution  of  coal  by  means  of  a  hand  shovel, 
through  an  opening  some  12  x  16  inches,  to  a  point  10 
feet  distant,  is  one  requiring  great  skill.  In  the  case  of 
caking  coals,  the  longer  the  fire  box  the  more  difficult  is 
the  task  of  breaking  up  the  fire  through  the  fire  door  open- 
ing. 

Q.  What  are  the  advantages  of  large  grate  area  ? 

It  lowers  the  rate  of  combustion,  and  thus  permits  the 
use  of  inferior  grades  of  fuel  which  could  not  be  economi- 
cally employed  in  locomotives  having  a  small  ratio  of  grate 
area  to  total  heating  surface. 


250  COMBUSTION    OF   COAL. 

For  locomotives  of  great  power,  a  large  grate  surface  is 
essential,  even  under  the  highest  economical  rates  of  com- 
bustion, and  for  this  reason  boilers  with  an  extended  grate 
surface,  such  as  the  Wootten,  become  more  or  less  a 
necessity. 

Q.  What  is  the  rate  of  combustion  in  locomotive  boiler 
practice  ? 

The  rate  of  combustion  will  vary  with  the  type  and  size 
of  locomotive,  the  contour  of  the  railroad,  the  weight  and 
speed  of  trains,  etc.  From  80  to  125  pounds  may  fairly 
represent  ordinary  practice,  but  the  extreme  limit  to 
economical  combustion  appears  to  be  about  150  pounds 
per  square  foot  of  grate  surface  per  hour ;  a  higher  rate  of 
combustion  is  apt  to  lift  the  coal  from  the  grates  and  loss 
of  efficiency  occurs. 

Q.  What  is  the  special  function  of  the  fire-brick  arch 
in  locomotive  fire  boxes  ? 

The  supplying  of  fuel  in  a  locomotive  fire  box  is  an 
intermittent  operation;  consequently,  the  temperature  of 
the  fire  is  constantly  changing  from  high  to  low,  depend- 
ing upon  the  quantity  of  fresh  fuel  laid  upon  the  fire. 
The  fire-brick  arch  gets  white  hot  by  reason  of  its  posi- 
tion over  the  fire;  this  stored-up  heat  assists  in  driving 
out  the  volatile  combustible  matter  in  the  fuel ;  as  there 
is  almost  always  an  excess  of  air  passing  through  the  fire, 
the  gases  driven  off  by  the  combined  heat  of  the  fire  and 
the  incandescent  fire-brick  arch  are  raised  to  a  very  high 
temperature  while  in  intimate  contact  and  mixture,  com- 
bustion ensues  under  the  most  favorable  conditions  for 
completeness,  economy,  and  high  temperature.  The  prod- 
ucts of  combustion  are  then  diverted  to  the  rear  of  the 


BRICK   ARCH    FOR   LOCOMOTIVES. 


251 


fire  box,  where  a  change  of  direction  is  necessary  before 
passing  forward  toward  the  tubes. 

By  its  use  the  combustion  of  bituminous  coal  is  im- 
proved, smoke  is  prevented,  cinder  sparks  are  arrested,  the 
flame  and  gases  from  the  fire  are  cleaner,  that  is,  carry 
less  soot  and  impurity,  the  dragging  of  the  fire  is  reduced, 
and  the  fuel  is,  therefore,  used  in  a  more  economical  man- 
ner  than  in  the  ordinary  fire  box. 

Q.  What  is  the  usual  construction  of  the  brick  arch  in 
locomotive  fire  boxes? 

The  brick  arch  consists  usually  of  fire-brick  tiles  laid  on 
tubular  bearing  bars.  Fig.  45  shows  one  form  of  con- 


FlG. 


struction  in  which  the  tubular  bearing  bars  are  secured  to 
the  tube  sheet  at  one  end,  the  other  end  being  secured  to 
the  crown  sheet.  There  is  a  water  circulation  through 
these  pipes  which  prevents  their  burning  out  in  the  fur- 
nace. Another  design  is  shown  in  Fig.  46,  in  which  the 
tubular  bearing  bars  extend  the  whole  length  of  the  fire 
box,  the  water  connection  being  such  that  a  constant  cir- 
culation is  had.  The  fire-brick  tiles  extend  across  the 
fire  box  from  side  to  side ;  the  arch  is  lowest  next  the  tube 


252  COMBUSTION    OF    COAL. 

sheet,  and  inclines  upward  as  it  approaches  the  rear  end 
of  the  fire  box ;  the  length  of  the  arch  and  angle  of  incli- 
nation vary  with  the  size  of  the  fire  box,  but  the  rear  end 
must  always  be  high  enough  properly  to  feed  and  care  for 
the  fire. 

Another  method  of  construction  is  to  build  a  curved 
arch  across  the  fire  box  from  side  to  side,  as  shown  in  Figs. 
68  and  69. 

^.  Does  the  brick  arch  cause  leaky  flues? 

This  question,  raised  by  M.  D.  Corbus,  in  Locomotive 
Engineering  (January,  1900),  is  accompanied  by  the  state- 


FlG    46. 

ment  that  practice  has  demonstrated  positively  in  some 
locomotives  that  a  brick  arch  in  a  fire  box  causes  the  flues 
to  leak,  beginning  directly  after  the  arch  is  put  in,  and  the 
engine  does  hard  labor.  The  arches  as  described  by  him 
are  in  three  pieces,  placed  lengthwise  in  the  fire  box  and 
resting  on  four  plugs  screwed  into  the  side  sheets.  The 
brick  is  cut  away  next  the  flue  sheet  and  side  sheets,  to 
allow  cinders  and  fine  coal  to  drop  down  to  the  grates ; 


FIRE-BRICK   ARCHES.  253 

only  about  6  inches  of  each  corner  of  the  arch  rests  against 
flue  sheet,  from  6  to  10  inches  below  the  flues. 

In  replying  to  the  above,  George  B.  Nicholson,  through 
the  same  journal,  asks:  What  causes  flues  to  leak?  Is  it 
not  a  too  rapid  expansion  and  contraction  of  the  metals  of 
the  flue  sheet  and  flues  ?  Then  will  a  brick  arch  cause  this 
expansion  and  contraction  ?  Suppose  an  engine  with  a 
brick  arch  to  be  fired  up  and  gradually  heated  to  the  work- 
ing point,  the  heat  of  the  fire  box  probably  being  between 
2,000°  and  2,500°  F.  The  brick  arch  attains  and  will  hold 
this  temperature  for  a  considerable  time  after  the  fire  has 
been  knocked  out  of  the  engine.  Now  this  brick  arch, 
representing  an  almost  fixed  number  of  heat  units,  is 
placed  within  from  4  to  6  inches  of  the  flues  and  flue 
sheet;  there  is  nothing  about  this  that  iz  likely  to  cause 
an  undue  variation  in  the  temperatures  of  either.  The 
real  reason  is  that  the  fire  is  not  maintained  under  the 
flues  as  it  should  be,  quite  frequently  getting  into  such  a 
condition  that  cold  air  is  drawn  rapidly  through  the  grates 
and  up  through  the  flues ;  the  flow  may  last  but  a  few 
seconds,  still  long  enough  considerably  to  reduce  the  tem- 
perature of  the  metals ;  it  is  then  cut  off  by  the  applica- 
tion of  a  shovelful  of  green  coal  when  the  great,  almost 
permanent  heat  of  the  arch  will  cause  the  temperature  to 
rise  much  more  rapidly  than  would  be  the  case  in  waiting 
for  the  coal  to  ignite,  and  the  heat  of  the  fire  cause  the 
change.  This,  being  repeated  from  time  to  time,  starts 
the  flues  to  leak ;  the  engine  is  brought  in,  the  arch 
knocked  out  and  condemned,  when  the  trouble  was  not  the 
arch,  but  in  the  method  of  firing. 

If  brick  arches  are  put  in  with  just  enough  space  be- 
tween the  arch  and  flues  to  permit  of  the  free  circulation 
of  the  gases,  and  at  the  same  time  not  to  allow  the  opening 


254 


COMBUSTION   OF   COAL. 


to  become  blocked  with  cinders,  and  high  enough  that  a 
good  fire  can  be  kept  under  them  with  reasonable  ease,  a 
decided  improvement  in  steaming  qualities  will  be  secured, 
as  well  as  lessened  fuel  consumption  and  increased  life  of 
the  flues. 

Q.  What  kind  of  grates  are  commonly  supplied  locomo- 
tive fire  boxes? 

The  present  practice  is  confined  almost  wholly  to  shak- 
ing grates,  because  of  the  facility  afforded  for  cleaning  the 
fire  on  the  road,  and  for  dumping  the  contents  of  the  fire 
box  at  the  end  of  the  trip. 

Q.  What  is  the  construction  of  the  tubular  water 
grate  ? 

The  water  grate  consists  of  tubes  extending  from  the 
tube  sheet  in  the  fire  box  to  the  opposite  sheet  at  the  rear, 


J — L 


I 


FIG,  47,  A.— Plan. 


as  shown  in  Fig.  47.  These  water  tubes  are  placed  side  by 
side  across  the  width  of  the  fire  box  with  such  interval 
between  them,  for  air  space,  as  shall  best  adapt  them  for 
the  fuel  to  be  used ;  they  usually  incline  slightly,  to  give 


PLAIN    FIRE    GRATE. 


255 


better  circulation  than  when  laid  horizontally.      The  circu- 
lation of  water  through  these  tubes  prevents  their  burn- 


oooooooooooo 
ooo   ooooooooo 


FIG.  47,  B.— Longitudinal  Section. 


mi 

0000 

o   o    o    o   o 

oooooc 

o    o    o   o    o 

O       0       0       0 

o   o    o    o   o 

)OOOOO 

00000 

m 
<m 

•m. 

TMk 
WA 

FIG.  47.  C.— Cross  Section. 

ing  out,  unless  they  become  filled  with  scale,  which  is  a 
not  infrequent  occurrence. 

Q.  What  are  the  ordinary  details  of  a  locomotive  fire- 
box grate  ? 

For  coal-burning  locomotives  the  grates  in  use  include 
the  plain  grate  bars  with  drop  plate  for  the  removal  of 
ashes,  etc. ,  at  the  end  of  the  run ;  such  a  grate  is  shown 
in  Fig.  48,  in  which  i  represents  the  grate  bars;  2,  a 
dead  plate;  3,  the  end  holder;  4,  the  drop  plate;  5,  the 
drop-plate  handle ;  6,  the  drop-plate  handle  supports ;  7, 
the  drop-plate  shaft ;  8,  the  drop-plate  shaft  bearing. 

Shaking  grates  are  now  in  very  general  use  in  locomo- 
tive practice.  The  ordinary  details  are  much  the  same 
for  all  grates,  but  there  is  a  wide  diversity  in.  minor  de- 
tails. Fig. 49,  from  Grimshaw's  "  Locomotive  Catechism," 
shows  the  salient  points  of  shaking-grate  mechanism  as 


256 


COMBUSTION    OF    COAL. 


ordinarily  applied  to  locomotives,  in  which  i  represents  a 
series  of  grates,  each  consisting  of  a  central  bar  with  rin- 
gers passing  each  other,  with  suitable  air  space  between, 


SHAKING  GRATE. 


257 


the  whole  forming  when  in  normal  condition  a  flat  surface 
for  the  fuel ;  2,  the  frame  carrying  the  rocking  grates ;  3, 
a  connecting  bar  by  which  all  the  rocking-grate  bars  are 


258  COMBUSTION   OF   COAL. 

operated  simultaneously;  4,  a  lever  extending  up  into  the 
cab  for  operating  the  grates;  5,  a  connecting  link;  6,  a 
lever  handle,  removable;  7,  a  drop  plate  to  facilitate  clean- 
ing the  fire  box  of  unburned  fuel,  ashes,  and  clinkers ;  8, 
drop-plate  rod;  9,  drop-plate  crank;  10,  drop-plate  crank 
handle;  n,  drop-plate  crank  bearing. 

Q.  How  do  anthracite  and  bituminous  coals  compare  in 
evaporative  power  in  locomotive  practice  ? 

It  would  naturally  be  expected  that  as  anthracite  is 
richer  in  carbon  than  the  average  quality  of  bituminous 
coal  (82  and  58  per  cent,  respectively,  being  the  mean  of 
several  analyses),  anthracite  coal  should  yield  a  higher 
evaporative  duty.  Service  trials,  however,  prove  that  the 
difference  existing  is  wholly  in  favor  of  bituminous  coal, 
fully  bearing  out  the  assertion  frequently  made  by  firemen, 
that  a  tender  load  of  soft  coal  will  go  further  than  a  like 
quantity  of  hard  coal. 

Recent  experiments  on  the  N.  Y.,  L.  E.  and  W.  R.R., 
with  high -class  modern  locomotives,  gave  evaporative  rates 
from  and  at  212°  F.  per  pound  of  coal,  of  5.68  for  an- 
thracite and  7.2  for  bituminous. 

The  theoretical  evaporative  power  of  anthracite  coal  con- 
taining 82  per  cent  of  carbon  and  7.4  per  cent  of  volatile 
matter  is  15.25  pounds,  from  and  at  212°  F. ,  while  that  of 
bituminous  coal  containing  58  per  cent  of  carbon  is  about 
1 2  pounds,  due  allowance  being  made  for  other  component 
parts  (Dixon). 

Q.  Is  the  ordinary  operation  of  a  locomotive  boiler 
favorable  to  high  duty  ? 

The  operation  of  a  locomotive  boiler  militates  against  a 
high  duty;  its  exposure  to  constantly  changing  atmos- 


SINGLE-SHOVEL    FIRING.  259 

pheric  conditions  cannot  but  be  a  fruitful  source  of  loss, 
and  the  remarkable  differences  of  opinion  with  regard  to 
boiler  proportions,  grates,  and  draft  appliances,  prove  that 
some  boilers,  at  least,  do  not  have  a  fair  chance  to  per- 
form their  functions  in  an  economical  manner.  The  effi- 
ciency of  a  well-designed  bituminous  coal-burning  boiler 

72^1 OO 

may  be  taken  at :  -  -  =  60  per  cent,  which,  consid- 

ering the  disadvantages  under  which  it  labors,  is  a  cred- 
itable figure  (Dixon). 

Q.  What  evaporative  performances  are  had  of  locomotive 
boilers  in  practice  ? 

From  a  number  of  locomotive  tests  made,  rather  to  test 
the  coal  than  to  test  the  locomotive,  evaporations  are  shown, 
according  to  W.  O.  Webber,  from  6^  to  8j4  and  9  pounds 
of  water  per  pound  of  combustible,  and  the  fuel  consumed 
per  square  foot  of  grate  surface  90  pounds,  and  running 
from  there  to  136  pounds.  These  engines  were  small; 
one  on  which  most  of  the  tests  were  made  was  an  engine 
with  a  fire  box  only  3  feet  wide  by  5  feet  long,  with  a 
boiler  42  inches  diameter,  114  2-inch  flues,  2^  inch  ex- 
haust nozzle.  Engine  15"  x  22",  and  only  740  total 
square  feet  of  heating  surface.  The  standard  American 
locomotive  will  develop  on  an  average  a  horse-power  for 
each  27  pounds  of  water  evaporated  when  not  overloaded; 
the  evaporation  under  ordinary  conditions  will  run  from 
5/^  to  6I/2  pounds  of  water  per  pound  of  coal. 

Q.  What  are  some  of  the  practical  results  of  single- 
shovelful  firing  ? 

Mr.  Angus  Sinclair's  observations  while  riding  on  loco- 
motives on  the  B.,  C.  R.  and  N.  Ry.,  where  firing  tests  were 


260  COMBUSTION    OF   COAT,. 

being  made,  was  that  the  coal  was  broken  to  small  lumps, 
and  the  fireman  kept  up  the  necessary  supply  of  fuel  in 
the  fire  box  by  putting  on  a  single  shovelful  at  a  time. 
When  the  engine  with  a  long  freight  train  was  pulling 
hard  on  a  long  grade,  the  coal  thrown  into  the  fire  box 
averaged  5  shovelfuls  per  mile,  each  containing  about 
1 8  pounds  of  coal,  which  was  90  pounds  to  the  mile.  On 
the  level  it  was  about  5  shovelfuls  for  every  two  miles. 
The  fire  always  looked  clear  and  bright,  and  all  the  en- 
gines steamed  admirably.  The  engineer  always  filled  up 
the  boiler  well  going  into  a  station,  and  then  shut  off  the 
injector  for  a  few  minutes  in  starting,  to  let  the  fireman 
make  up  a  good  fire.  As  soon  as  the  train  was  going  the 
engineer  hooked  up  the  engine  as  far  as  he  could  to  avoid 
tearing  the  fresh  fire  to  pieces.  When  the  engine  was 
running  for  a  grade,  a  fairly  heavy  fire  was  gradually  put 
upon  the  grates,  and  it  was  maintained  during  the  heavy 
pull ;  but  was  made  up  by  single  shovelfuls,  or,  at  most, 
two  shovelfuls  at  one  time.  There  were  no  special  smoke- 
preventing  appliances  used;  the  fire  boxes  were  supplied 
with  a  brick  arch,  but  no  means  were  employed  to  admit 
air  above  the  fire. 

Q.  Is  there  a  saving  in  coal  by  light  firing  in  loco- 
motive practice  ? 

Mr.  Fred  McArdle,  an  engineer  on  the  B. ,  C.  R.  and 
N.  Ry. ,  writes  that  the  single-shovelful  method  of  firing 
has  brought  about  a  great  saving  in  coal,  making  less  work 
for  the  fireman,  and  more  pleasant  for  the  engineer.  The 
engine  is  not  popping  off  continuously  while  standing  at 
stations.  The  cab  and  train  are  not  smothered  in  dense 
black  smoke  from  the  time  the  engine  is  shut  off  until  the 
train  is  again  started.  Prior  to  the  time  that  light  firing 


BEST    METHOD    OF   FIRING.  261 

was  adopted  passenger  engines  were  fired  with  three  to 
five  shovels  of  coal  to  a  fire ;  the  same  engines  are  now 
fired  with  one  shovel  of  coal  to  a  fire,  and  at  no  time  ex- 
ceeding two,  and  they  only  when  starting  away  from  sta- 
tions and  going  over  heavy  grades.  At  the  present  time 
engines  are  running  from  155  to  250  miles  without  taking 
coal,  and  savings  of  2  to  3}^  tons  of  coal  are  now  effected 
on  each  round  trip.  The  trains  are  from  3  to  6  coaches ; 
engines  15x24  to  17x24  inches.  Through  freight  en- 
gines on  all  divisions  are  18x24—6  wheel  connected, 
fired  with  one  and  two  shovels  to  a  fire,  rarely  throwing 
out  black  smoke  between  stations;  they  run  96  to  105 
miles  with  one  tank  of  coal.  These  trains  save  2  to  4 
tons  of  coal  each  round  trip  over  the  former  method  of 
firing. 

Q.  What  is  the  best  method  of  firing  a  locomotive  ? 

Referring  again  to  Mr.  McArdle's  communication,  he 
made  the  excellent  suggestion  that  to  make  a  success  of 
light  firing  the  engineer  and  fireman  must  work  together. 
The  fireman  should  carry  a  clean,  light  fire,  keeping  the 
fire  thin  enough  for  .plenty  of  air  to  be  admitted  for  com- 
bustion. This  he  cannot  do  if  his  engineer,  in  starting, 
allows  his  lever  to  remain  at  full  stroke  for  a  quarter  of  a 
mile  before  he  begins  to  cut  it  back.  Under  such  condi- 
tions the  fireman  with  a  light  fire  would  have  very  little 
fire  left  in  his  box  by  the  time  the  train  had  moved  half 
its  length. 

Under  the  old  method  of  firing,  a  shovelful  of  coal  was 
put  in  each  corner  of  the  box,  and  one  or  two  down  in  the 
centre ;  that  method  of  firing  has  been  demonstrated  to  be 
a  mistake,  as  they  now  fire  the  same  engines  with  one  or 
two  shovels  of  coal  at  a  time. 


262  COMBUSTION    OF   COAL. 

Q.  What  are  the  noticable  improvements  in  connection 
with  light  firing  and  boiler  repairs? 

Mr.  Henry  Raps,  foreman  boilermaker  for  the  B.,  C.  R. 
and  N.  Ry.,  reports  freer  steaming  qualities;  longer  life 
and  more  uniform  wear  of  brick  arches ;  a  decrease  in  the 
number  of  burned  and  broken  grates ;  a  decrease  in  the 
number  of  bent  and  broken  ash-pan  dampers  and  their  fas 
tenings ;  a  fewer  number  of  stopped-up  flues  ;  a  longer  life 
of  nettings  and  stacks ;  the  total  absence  of  burned  smoke 
arches  and  extensions,  and  the  non-accumulation  of  cinders 
in  the  front  end. 

Q.  What  is  the  direct  saving  upon  the  brick  arches  by 
light  firing  ? 

On  account  of  fires  not  being  so  thick  in  light  firing, 
there  is  not  as  much  liability  to  throw  coal  against  the 
arch.  As  there  is  less  fire  to  clean  out  at  the  end  of  the 
trip,  there  is  less  danger  of  the  arch  being  struck  by  the 
clinker  bar ;  for  these  reasons  brick  arches  last  longer.  A 
comparison  maybe  instituted  thus :  51  brick  arches  ap 
plied  to  locomotives  under  the  old  method  of  firing  aver- 
aged 7,863  miles  per  arch. 

Forty-five  brick  arches  under  the  single-shovelful  method 
of  firing  averaged  9,703  miles  per  arch,  a  gain  of  more  than 
23  per  cent. 

The  average  cost,  including  maintenance,  of  one  arch 
under  the  old  method  of  firing  was  $6.41  ;  an  average  cost 
of  8TyF  cents  per  100  miles.  The  average  cost,  including 
maintenance,  of  one  arch  under  the  light  firing  was  $4.61 ; 
an  average  of  4^%  cents  Per  IO°  rniles. 

Q.  What  are  the  principal  furnace  details  of  the  Wootten 
boiler  ? 

Previously  to  the  invention  of  the  Wootten  boiler  by 


WOOTTEN    FIRE    BOX. 


263 


John  E.  Wootten,  in  1877,  it  had  been  the  general  prac- 
tice to  make  the  fire  boxes  of  locomotives  of  a  width  de- 
termined by  the  distance 
between  the  inner  faces 
of  the  opposite  driving 
wheels ;  Wootten's  in- 
vention consisted  in  in- 
creasing the  area  of  the 
grate  by  arranging  the 
fire  box  and  grate  above 
and  extending  them 
laterally  over  the  driving 
wheels,  without  raising 
the  body  of  the  boiler 
to  any  material  extent. 
Figs.  50  and  51  are 
reproductions  of  the 
original  patent  office 

drawing,  in  which  it  will  be  seen  that  the  fire  box  A  later- 
ally overhangs  the  driving  wheels  B,  B';  the  grate  D  also 
overhangs  the  wheels  and  extends  across  the  interior  of 


FIG 


FIG.  51. 


264  COMBUSTION    OF   COAL. 

the  fire  box.     The  ash  pan  G  collects  the  ashes  and  di- 
rects them  into  the  receptacle  //. 

A  bridge  wall  M  extends  across  the  fire  box  or  combus  • 
tion  chamber  and  may  be  either  a  water  space  or  made  of 
fire  brick;  this  bridge  wall  plays  an  important  part,  for  the 
grate  being  necessarily  elevated,  a  corresponding  elevation 
of  the  body  of  the  boiler  would  be  demanded  in  the  ab- 
sence of  the  bridge,  in  order  that  the  tubes  ;//  might  be 
at  a  proper  height  above  the  grate,  to  prevent  the  direct 
escape  of  fuel  through  the  tubes,  and  this  elevation  of  the 
body  of  the  boiler  would  render  the  boiler  topheavy. 
The  arrangement  of  the  bridge  wall,  as  shown,  permits  the 
placing  of  the  tubes  low  down  so  that  the  body  of  the 
boiler  may  be  as  low  as  usual,  and,  therefore,  not  top- 
heavy. 

Q.  What  advantages  were  attained  by  the  fire  box  de- 
signed by  Wootten  ? 

Important  advantages  are  attained  by  the  increased 
grate-bar  area  due  to  the  lateral  extension  of  the  fire  box. 
The  fuel  can  be  consumed  in  comparatively  thin  layers 
more  gently  and  economically,  and  with  less  injury  to  the 
fire  box  than  the  thick  mass  of  intensely  heated  fuel  in  an 
ordinary  contracted  fire  box.  The  increased  grate  area 
dispenses  with  the  usual  contracted  exhaust  opening  for 
creating  an  artificial  draft,  a  larger  exhaust  opening  being 
adopted,  and,  consequently,  the  tearing  up  of  the  fuel  in 
the  firebox  is  avoided,  the  forcible  expulsion  of  hard  par- 
ticles of  fuel  through  the  tubes,  and  the  consequent  waste 
of  fuel,  is  prevented,  and  the  usual  spark-arrester  dis- 
pensed with ;  these  advantages  are  attained  without  ren- 
dering the  locomotive  topheavy  by  the  combination  of  the 
laterally  extended  fire  box  with  the  bridge  M. 


WOOTTEN    FIRE    BOX. 


265 


Q.  Was  the  combination  of  bridge  wall  and  combustion 
chamber  adhered  to  in  the  Wootten  boiler  ? 

In  1886,  Wootten  patented  another  firebox  in  which  the 
combustion  chamber,  which  formed  so  prominent  a  feature 


FIG. 


in  the  original  patent,  was  dispensed  with,  and  a  bridge 
wall  only  employed ;  this  design  in  one  of  several  forms 
is  shown  in  Figs.  52,  53,  and  54,  and  consists  of  a  fire 
bridge  located  wholly  within  the  fire  box  and  supported 


FIG.  53. 


266 


COMBUSTION    OF   COAL. 


above  the  grate  in  such  relation  to  the  tube  sheet  as  to 
form  a  space  or  chamber  in  the  rear,  which  is  closed  at  the 
bottom  and  open  at  the  top,  for  the  free  passage  of  the 
products  of  combustion  from  the  fire  box  to  the  tubes. 

This  later  design,  while  retaining  to  a  substantial  de- 
gree the  advantageous  features  of  wide  fire-box  boilers,  by 
this  time  approved  in  practical  service,  affords  the  advan- 
tages of  a  reduction  in  cost  and  an  increased  amount  of 


FIG.  54. 

area  of  tube-heating  surface  relatively  thereto.  The  fire 
bridge  can  be  readily  applied  and  fitted  in  position  and  is 
conveniently  accessible  for  renewal  and  repair,  and  the 
grate  area  attainable  in  boilers  of  this  type  is  so  ample 
that  no  objection  results  from  such  curtailment  as  is  in- 
volved in  locating  the  fire  bridge  and  combustion  space 
within  the  fire  box  and  above  a  portion  of  the  grate. 

Q.  What  are  the  disadvantages  of  a  wide  fire  box? 

Fault  has  been  found  with  wide  fire  boxes  because  of 
their  supposed  greater  liability  to  leakage  by  reason  of  ex- 
pansion and  contraction;  but  the  real  reason  for  leaky 
joints,  broken  stay  bolts,  etc.,  which  caused  much  annoy- 


BARNES    LOCOMOTIVE    BOILER.  267 

ance  with  the  earlier  Wootten  fire-box  designs,  was  due 
rather  to  the  flat  surfaces  and  other  defects  in  the  general 
design,  than  is  traceable  to  large  grate  area,  apart  from 
other  considerations. 

Q.  What  advantages  are  claimed  for  the  division  of 
the  wide  fire  box  into  two  separate  furnaces  ? 

In  many  instances,  especially  where  the  fuel  employed 
is  of  low  grade,  free  burning,  and  contains  a  considerable 
percentage  of  hydrocarbons  tending  to  evolve  smoke,  the 
use  of  two  furnaces  has  been  deemed  desirable,  provided 
it  can.be  accomplished  without  undue  expense  or  compli- 
cation of  construction,  or  incidental  curtailment  of  grate 
area  to  any  objectionable  degree.  Two  furnaces  permit  of 
a  better  system  of  alternate  firing,  and  thus  reduce  the  in- 
tensity of  smoke  when  burning  bituminous  coals  of  low 
grade,  than  is  the  case  with  a  single  fire  box  under  ordi- 
nary conditions. 

Q.  What  are  the  general  details  of  the  fire  box  of  the 
Barnes  locomotive  boiler? 

This  boiler  is  of  the  wide  fire-box  type,  in  which  a 
laterally  extended  fire  box  and  a  combustion  chamber  are 
provided.  At  the  rear  end  of  the  combustion  chamber  is 
a  water  wall,  which  is  open  at  the  bottom  to  the  water 
space  in  the  waist  below  the  combustion  chamber,  and  ex- 
tends a  sufficient  distance  above  the  bottom  of  the  com- 
bustion chamber  to  serve  as  the  forward  boundary  wall  of 
the  bed  of  fuel  on  the  grate  (see  Fig.  55).  The  interior  of 
the  fire  box  is  divided  into  two  separate  and  independent 
furnaces,  by  a  central  longitudinal  water  wall,  which  is 
closed  at  bottom  by  a  water- space  bar,  and  at  its  front  end 
is  open  at  bottom  to  the  waist  of  the  boiler  and  to  the 


268 


COMBUSTION   OF   COAL. 


FIG.  55. 


water  wall  above  referred  to,  Fig.    56.      In  the  case  of  a 
double  combustion  chamber,  as  in    Fig.    57,  the  central 


OOO  OO 
O  O  OOO 
OOOO 


o  o  o  o  o 

D  O  O  OO  O., 

o  o  o  o  o  ''•'  '• 

OOO  O/'/'' 


FIG.  56. 


BARNES    LOCOMOTIVE    BOILER. 


269 


water  wall  is  open  to  the  waist  at  both  top  and  bottom. 
The  side  sheets  of  the  water  wall,  in  the  middle  of  the 
furnace,  are  connected  at  their  upper  ends  to  the  crown 


FIG.  57. 


sheets  of  the  furnaces,  or  may  be  made  integral  with  the 
crown  sheets  as  shown  in  the  engraving.  Fig.  57  shows 
in  plan  the  double  combustion  chamber,  and  Fig.  58  a 
single  combustion  chamber  common  to  both  furnaces.  A 


2/0 


COMBUSTION    OF   COAL. 


material  increase  of  fire-box  heating  surface  is  provided 
by  the  central  water  wall.  By  the  use  of  the  two  independ- 
ent  furnaces,  the  fire  may  be  kept  in  better  condition  than 
is  practicable  with  a  single  and  exceptionally  large  furnace. 


FIG.  58. 

Q.  What  is  the  best  modern  practice  in  the  means 
adopted  to  increase  the  production  of  steam  by  increased 
draft  in  locomotives? 


EXHAUST    PIPES   AND    TIPS.  2/1 

Mr.  C.  H.  Quereau,  Denver  and  Rio  Grande  R.  R.,  ob- 
tained data  for  the  Sixth  Session  of  the  International 
Railway  Congress,  from  the  Motive  Power  Departments 
of  railroads  owning  some  15,000  out  of  more  than  36,000 
locomotives  in  use  in  the  United  States,  Canada,  and 
Mexico ;  these  results  are  given  in  the  following  ten  ques- 
tions. 

Q.  What  evaporative  results  are  had  in  average  loco- 
motive practice  ? 

Coal,  with  evaporative  results  varying  from  10.76  to 
3. 10  pounds  of  water  per  pound  of  coal,  is  the  almost  uni- 
versal fuel,  though  in  the  West,  where  the  quality  of  the 
coal  is  poor  and  the  cost  high,  fuel  oil  is  used  success- 
fully. 

Q.  What  is  the  present  tendency  as  between  single  or 
double  exhaust  pipes  ? 

The  single  exhaust  pipe  is  evidently  the  preference  of 
most  roads  and  apparently  is  displacing  the  double  pipe. 
There  has  been  a  very  decided  shortening  of  the  length 
of  the  pipe  during  the  past  ten  years,  notwithstanding 
that  the  average  diameter  of  the  smoke  box  must  have 
increased  in  the  same  period.  Because  of  the  very  gen- 
eral adoption  of  this  change  and  the  considerable  amount 
the  pipes  have  been  shortened,  it  seems  reasonable  to  as- 
sume that  it  must  have  been  noticeably  beneficial. 

Q.  What  is  the  most  efficient  form  of  exhaust  tip  ? 

The  tip  shown  at  b,  Fig.  59,  is  essentially  that  recom- 
mended by  the  Master  Mechanics'  committee.  That  60 
per  cent  of  the  roads  reporting  use  this  form  as  standard 
is  presumptive  evidence  that  it  is  the  most  efficient  form. 
The  tips,  c  and  d ,  vary  but  little  from  a  in  the  shape  of 


272 


COMBUSTION    OF   COAL. 


the  exhaust  and  the  absence  of  a  shoulder,  which  must 
produce  back  pressure.  If  these  are  classed  with  b,  the 
result  is  that  84  per  cent  of  the  tips  have  no  shoulder.  A 
reasonable  interpretation  of  these  facts  is  that  tips  with 
shoulders  are  less  efficient  than  those  without.  There  is 
one  advantage  in  the  shouldered  tip;  namely,  that  it  will 
not  gum  up  by  the  accumulation  of  oil  from  the  exhaust. 

There  are  good  reasons  for  the  extensive  use  of  the  sin- 
gle exhaust  tip,   which  presupposes  the  use  of  a  single 


a 


D  U 


FIG.  59. 


exhaust   pipe.      The  following  table   gives  the   areas  in 
square  inches  of  different  tips : 


AVERAGE  EXHAUST  TIPS. 


Cylinders. 

SINGLE. 

DOUBLE. 

Diameter. 

Area. 

Diameter. 

Area. 

17  X  24  in 

4Xin- 
4^   " 
4#   " 

5 
5 

14.2  sq.  in. 
15-9       " 
17.7 
19.6 
19.6      " 

?>Y&  in. 
3tt   " 
3tt  " 
3tt  - 

3/2     " 

7.7  sq.   in. 
8.9        " 

8-9        " 
8.9        " 
9.6       '• 

18  X  24    "  
19  X  24   "  

20  X  24    *  '  

20  X  26   " 

The  area  of  the  single  exhaust  tip  is  shown  to  be  rough- 
ly twice  that  of  the  double  tip.  It  is  reasonable  to  as- 
sume that  each  is  as  large  as  it  can  be  made,  and  produces  a 


BEST   FORM    OF    STACK.  273 

satisfactory  amount  of  steam  under  service  conditions ;  also 
that  two  cylinders  exhausting  alternately  through  a  single 
tip  will  meet  less  resistance,  hence  produce  less  back 
pressure,  than  the  same  cylinders  exhausting  each  through 
a  separate  tip  half  the  area  of  the  single  tip ;  hence,  that 
the  single. tip  is  more  efficient  than  the  double.  This 
conclusion  would  be  unwarranted  unless  it  had  been  shown 
that  with  the  single  exhaust  pipe  and  tip  and  a  partition  of 
the  proper  height  between  the  exhausts,  the  exhausts  from 
one  cylinder  do  not  interfere  with  those  from  the  other. 
The  use  of  a  bridge  or  bar  in  the  exhaust  tip  is  universally 
condemned,  except  as  a  temporary  expedient. 

Q.  What  is  the  best  form  of  stack? 

The  cast-iron  choke,  or  tapered  stack,  is  the  choice 
of  80  per  cent  of  the  roads  reporting,  and  growing  in 
favor. 

There  is  also  an  increasing  tendency  to  reduce  the  di- 
ameter of  the  stack,  the  cylinders  remaining  the  same. 
The  diamond  stack  is  standard  on  but  one  railroad 
system,  and  it  is  a  significant  fact  that  two  roads,  which 
at  one  time  were  under  the  control  of  the  system  on  which 
the  diamond  stack  is  standard  and  inherited  it,  have  begun 
to  discard  the  diamond  stack  for  the  tapered  design.  From 
these  facts  it  seems  reasonable  to  conclude  that  experience 
has  shown  the  diamond  stack  to  be  less  efficient  than 
either  the  straight  or  taper  form.  With  the  diamond 
stack  the  exhaust  steam  cannot  escape  in  a  direct  line  be- 
cause of  the  cone,  and  the  netting  area  through  which  the 
gases  must  escape  is  less  than  with  either  of  the  others. 

There  appear  to  be  no  rules  for  varying  the  stack  di- 
mension for  different  sizes  of  cylinder.  It  is  evident  that 
the  rule  given  by  the  Master  Mechanics'  committee  con- 
18 


2/4  COMBUSTION   OF   COAL. 

earning  the  best  relation  between  the  stack  and  the  ex- 
haust tip  has  had  considerable  influence.     See  Fig.  66. 

Q.  What  is  the  function  of  the  diaphragm  in  the  smoke 
box? 

The  chief  function  of  the  diaphragm,  which  is  used  only 
with  straight  or  tapered  stacks,  is  to  regulate  the  distri- 
bution of  the  draft  through  the  flues  and  grates.  They 
are  used  incidentally  to  extinguish  and  break  the  sparks 
coming  through  the  flues.  The  Michigan  Central  has 
increased  their  efficiency  in  this  respect  by  lining  the  sur- 
faces of  the  baffle  plates  against  which  the  sparks  strike 
with  steel  netting,  having  2^2  x  2^2  meshes  per  square 
inch,  and  wire  o.  109  inch  in  diameter.  These  functions 
apply  both  to  the  diaphragms  wholly  back  of  the  exhaust 
pipe  and  to  those  extending  in  front  of  the  exhaust  pipe. 
The  advantage  claimed  for  the  latter  over  the  former  is 
their  action  in  sweeping  practically  all  the  cinders  from 
the  smoke  box.  The  Chicago  Great  Western  has  found 
that  the  diaphragm  when  extending  forward  of  the  exhaust 
pipe  causes  excessive  wear  to  both  this  and  the  steam 
pipes. 

Q.  What  advantages  are  to  be  gained  by  the  use  of 
draft  pipes  ? 

The  use  of  draft  pipes  with  extension  front  ends  has 
increased  considerably  during  the  past  few  years.  There 
can  be  little  reason  for  doubt,  judging  by  the  reports,  that 
their  use  materially  increases  the  draft,  which  must  result 
in  increasing  the  efficiency  of  the  exhaust  by  allowing  an 
increase  in  the  diameter  of  the  tip  and  the  consequent  re- 
duction in  back  pressure.  On  the  other  hand,  there  is  no 
doubt  that  this  advantage  is  accompanied  by  occasional 


SMOKE-BOX    EXTENSION.  2/5 

delays  for  lack  of  steam,  due  to  the  petticoat  pipes  work- 
ing out  of  adjustment  or  becoming  warped  by  heat.  Such 
delays  are  frequently  due  to  poor  designs,  and  more  fre- 
quently to  carelessness  on  the  part  of  roundhouse  men 
whose  duty  it  is  to  adjust  these  parts,  but  a  certain  amount 
of  such  careless  work  can  never  be  entirely  obviated,  be- 
cause of  the  class  of  men  to  which  this  work  must  almost 
necessarily  be  intrusted.  Again,  it  is  entirely  probable 
that  a  considerable  number  of  these  delays  are  not  known 
to  the  heads  of  the  motive  power  departments. 

Q.  What  is  the  object  in  the  smoke-box  extension  of 
locomotives  ? 

The  original  purpose  for  which  the  extended  front  end 
was  designed  was  to  serve  as  a  receptacle  for  cinders  (see 
Fig-  63).  That  it  is  not  very  efficient  in  accomplishing 
this  end  was  shown  by  the  results  of  a  test  with  the 
mounted  locomotive  at  Purdue  University.  The  locomo- 
tive tested  had  1 7. 5  square  feet  of  grate  area,  and  a  front 
end  52  inches  in  diameter  by  64  inches  long,  including  the 
extension;  cylinders,  17x24  inches;  exhaust  tip  double, 
each  3  inches  in  diameter.  The  average  speed  in  miles  per 
hour  was  25,  and  the  duration  of  the  test  six  hours,  mak- 
ing it  equivalent  to  a  run  of  1 50  miles.  As  the  locomo- 
tive was  mounted  on  wheels  controlled  by  friction  brakes, 
and  did  not  move  in  relation  to  the  earth,  the  opportunities 
for  making  accurate  observations  and  measurements  were 
all  that  could  be  desired.  The  results  showed  that  75 
pounds  of  sparks  were  retained  in  the  front  end  at  the  end 
of  the  run,  while  294  pounds  had  passed  through  the 
stack. 

The  fact  that  sixteen  out  of  twenty-five  roads  reporting 
have  shortened  their  extensions  an  average  of  1 7  inches  in 


2/6  COMBUSTION    OF   COAL. 

the  past  ten  years  shows  quite  conclusively  that  experience 
has  demonstrated  it  does  not  accomplish  the  end  for  which 
it  was  designed,  or  that  the  gain  in  draft  by  shortening  is 
more  valuable  than  the  original  purpose. 

Q.  Does  the  efficiency  of  draft  appliances  in  locomotives 
vary  with  locality  or  with  quality  of  fuel  used? 

The  statement  has  frequently  been  made  that  draft  ap- 
pliances which  have  been  proved  by  extended  experience 
and  experiments  to  be  the  best  adapted  for  a  given  quality 
of  coal  or  section  of  the  country  do  not,  and  will  not, 
prove  at  all  adapted  for  similar  classes  of  coal  in  other 
sections,  and  that  it  is  necessary  to  use  entirely  different 
designs.  This  seems  an  unreasonable  proposition. 

The  sole  purpose  of  the  draft  appliances  is  to  produce 
a  vacuum  by  means  of  which  the  necessary  oxygen  for  the 
combustion  of  the  fuel  is  provided,  and  properly  to  distrib- 
ute this.  The  primary  source  of  the  forced  draft  neces- 
sary with  locomotives  is  the  force  of  the  exhaust  steam, 
and  the  most  efficient  design  of  draft  arrangements  is  that 
which  will  produce  the  required  vacuum  with  the  least 
loss  of  power,  that  is,  with  the  least  back  pressure.  As- 
suming that  such  a  design  has  been  devised  and  its  effi- 
ciency established,  it  follows  that  it  must  be  the  most 
efficient  whatever  the  locality  in  which  it  may  be  used, 
and  whatever  the  grade  of  coal,  and  the  only  reasonable 
change  in  the  design  which  should  be  allowed  is  to  in- 
crease or  decrease  the  vacuum  to  meet  the  necessities  of 
the  case  by  increasing  or  decreasing  the  back  pressure. 

No  claim  is  made  that  this  most  efficient  arrangement 
has  been  designed,  but  it  seems  reasonable  to  believe  it  is 
within  the  range  of  possibility,  and  when  designed  should 
be  universally  the  most  efficient.  For  instance,  it  having 
been  shown  that  the  shorter  the  front  end,  the  more  effi- 


DRAFT    IN    LOCOMOTIVES.  277 

cient  the  exhaust  jet  is,  this  remains  true  the  world  over, 
no  matter  what  the  fuel  or  other  conditions  may  be ;  as 
the  most  efficient  method  of  regulating  the  back  pressure 
has  been  shown  to  be  by  means  of  the  tip,  any  design 
which  fails  to  make  the  area  of  the  tip  less  than  that  of 
every  section  between  it  and  the  cylinder  must  be  faulty, 
wherever  used. 

,  Q.  What  conclusions  were  reached  by  Mr.  Quereau  re- 
garding the  means  adopted  to  increase  the  production  of 
steam  by  increased  draft  ? 

This  topic  naturally  falls  under  two  heads.     The  pro- 
ducing of  the  vacuum,  and  the  distribution  of  the  draft : 

The  Production  of  tJie  Vacuum. 

1.  The  most  efficient  means  of  producing  the  vacuum 
are  evidently  those  which  accomplish  the  result  with  the 
least  back  pressure  in  the  cylinders. 

2.  These  can  best  be  determined  with  a  locomotive  on 
a  testing  plant  where  the  conditions  can  be  made  those  of 
regular  service. 

3.  The  proper  basis  for  determining  efficiency  is  that 
which  compares  the  cause,  back  pressure,  with  the  result, 
vacuum,  and  conclusions  drawn  solely  from  the  vacuum 
obtained  are  of  doubtful  value. 

4.  The  steam  passages  from  the  cylinder  should  be  of 
ample  proportions. 

5.  The  exhaust  pipe  passages  should,  gradually  contract 
from  the  bottom  to  the  tip,  without  abrupt  curves. 

6.  The  area  of  the  opening  through  the  tip  should  be 
less  than  that  of  any  section  between  it  and  the  cylinder. 

7.  The  exhaust  pipe  should  be  single,  with  a  partition 
but  little  if  any  higher  than    13    inches,  and   the    total 


2/8  COMBUSTION   OF   COAL. 

height  as  short  as  possible  consistent  with  easy  curves  in 
the  pipe  and  a  proper  arrangement  of  the  netting,  provid- 
ing the  height  is  not  less  than  19  inches. 

8.  The  steam  passage  in  the  exhaust  tip  should  be  of 
the  shape  shown  at  b,  Fig.  59. 

9.  Crossbars  in  the  tip  lessen  the  efficiency  of  the  ex- 
haust jet. 

10.  The  front  end  should  be  as  short  as  possible. 

11.  With  front  ends  more  than  60  inches  in  diameter, 
double  draft  pipes  increase  the  efficiency,  but  careful  de- 
signing and  thorough  workmanship  are  necessary  to  pre- 
vent them  from  warping  and  working  out  of  ad j  ustment.     If 
they  become  displaced  they  are  worse  than  useless. 

12.  With  properly  designed  draft  pipes  it  is  probable 
that  the  greater  the  distance  from  the  exhaust  tip  to  the 
base,  or  choke,  of  the  stack  the  greater  the  efficiency. 

13.  Either  the  taper  or  straight  stack  is  more  efficient 
than  the  diamond  stack. 

14.  Probably  the  taper  stack  is  somewhat  more  efficient 
than  the  straight,  when  the  proportions  of  each  are  the 
best  for  any  given  case,  because  of  the  more  easy  approach 
and  exit  afforded  the  gases  by  the  former. 

15.  The  correct  rules  for  the  most  efficient  stack  pro- 
portions are  still  open  to  question. 

1 6.  The  theory  of  the  adjustable  exhaust  tip  is  admir- 
able, but  the  results  of  experience  have  been  that  those 
designs  tried  so  far  soon  become  inoperative.     To  be  per- 
manently successful  a  design  should  be  automatic  and  be- 
yond the  control  of  the  engineman — connected  with  the 
reversing  gear,  for  instance. 

17.  As  far  as  practicable  the  plane  of  the  netting  should 
be  at  right  angles  to  the  currents  of  gases  passing  through 
it,  so  as  to  offer  as  little  resistance  as  possible. 


PREVENTION   OF   FIRES   CAUSED   BY   SPARKS.       2 79 

1 8.  The  area  of  the  openings  through  the  netting  should 
be  greater  than  that  through  the  flues,  when  possible. 

The  Distribution  of  the  Draft. 

So  far  as  known  there  are  no  published  results  of  the 
most  efficient  arrangement  of  diaphragm  plates  or  draft 
pipes,  so  that  conclusions  concerning  them  are  largely 
matters  of  opinion  or  personal  experience. 

19.  With  diamond  stacks  the  distribution  of  the  draft 
is  best  accomplished  by  the  use  of  draft,   or  petticoat, 
pipes. 

20.  With   extended  front    ends  and   straight    or  taper 
stacks  the  baffle  plates  are  almost  entirely  depended  on  for 
regulating  the  distribution. 

21.  It  seems  entirely  probable  that  with  the  extended 
front  end  a  design  may  be  developed  which  will  leave  out 
the  baffle  plates  and  depend  entirely  on  draft  pipes  for  the 
distribution  of  the  draft,  and  that  such  a  design  would  be 
more   efficient   than   those  which  depend   on   the   baffle 
plates. 

Q.  What  conclusions  were  reached  by  Mr.  Quereau  re- 
garding the  means  for  preventing  fires  caused  by  sparks 
from  the  stack  ? 

The  following  conclusions  follow,  in  numerical  order, 
the  answers  to  the  previous  question : 

22.  The  extended  front  end  is  of  little  practical  use  as 
a  receptacle  for  cinders. 

23.  The  baffle  plates  and  netting  should  be  so  designed 
as  to  extinguish  the  sparks,  break  the  cinders  up,  and  then 
discharge  them  into  the  open  air. 

24.  Systematic  and  competent  inspection  of  front  end 
arrangments,  especially  the  netting,  at  regular  intervals, 


2.80  COMBUSTION    OF   COAL. 

in  connection  with  a  permanent  record  showing  the  condi- 
tion at  the  time  of  inspection  and  the  repairs  made. 

25.  The  use  of  fire  guards  made  by  ploughing  two  or 
three  furrows  as  far  from  the  track  as  possible,  and  then 
burning  over  the  ground  between  the  tracks  and  furrows. 

Q.  What  is  the  best  method  for  utilizing  the  heat  of 
exhaust  steam  in  locomotives  ? 

Mr.  Quereau  concludes  that : 

26.  American  practice  has  not  yet  developed  a  success- 
ful design  for  this  purpose,  though  two  roads  are  making 
the  attempt. 

27.  The  exhaust  from  the  air  pump  is  being  success- 
fully used  by  a  number  of  roads  to  heat  the  water  in  the 
tender. 

28.  Because  of  the  fact  that  most  American  locomo- 
tives are  equipped  with  injectors,  instead  of  pumps,  for 
feeding  the  boiler  with  water,  and  that  the  injectors  will 
not  work  with  feed  water  hotter  than  about   120°   F.,  it 
seems  probable  that  the  maximum  benefits  of  heating  the 
feed  water  by  means  of  the  air-pump  exhaust  will  not  be 
derived  till  the  control  of  the  temperature  of  the  feed 
water  is  made  automatic.     Experiments  with  this  end  in 
view  are  being  made. 

Q.  What  are  the  details  of  construction  of  the  Strong 
locomotive  fire  box  ? 

The  corrugated  fire  box  adopted  for  the  Strong  locomo- 
tive boilers  is  a  somewhat  radical  departure  from  the  de- 
signs which  have  long  been  employed  in  locomotive  con- 
struction. By  reference  to  Figs.  60,  61,  62,  it  will  be 
seen  that  there  are  two  corrugated  furnaces,  which,  by 
means  of  a  junction  piece,  lead  into  a  single  corrugated 
combustion  chamber,  the  latter  terminating  in  the  back 


STRONG'S  LOCOMOTIVE  FIRE  BOX. 


281 


tube  sheet,  from  which  the  tubes  proceed  forward,  as  in 
the  ordinary  locomotive,  to  the  smoke  box. 

The  ordinary  soft-coal  burning  boiler  52  inches  in  di- 
ameter has  about  900  stay  bolts,  but  this  boiler  has  none 
whatever.  There  is  not  a  rigid  connection  between  the 


FIG.  60. 

inner  and  outer  parts  of  the  boiler,  and  only  two  connec- 
tions of  any  kind  between  the  ends,  the  functions  of  which 
are  to  support  the  inner  shell;  there  is  nothing  whatever 
to  resist  expansion  and  contraction,  and  thus  hurtfully  act 
upon  the  material.  The  corrugations  doubtless  contribute 
to  freedom  of  movement,  but  even  if  they  do  not  the 


282 


COMBUSTION    OF    COAL. 


plates  of  the  outer  shell  have  the  usual  opportunity  to 
buckle. 

The  crown  sheet,  being  the  upper  half  of  a  cylinder, 
easily  parts  with  scale  which  may  form  upon  it,  and  in 
this  respect  is  in  direct  contrast  with  the  common,  flat 


^S*^^?^^^ 


FIG.  61. 

horizontal  crown  sheets  covered  with  bolts  and  crown  bars, 
which  are  a  sufficient  means  of  anchoring  all  scale  which 
forms  upon  the  sheet,  and  equally  efficient  means  of  pre- 
venting inspection  and  cleaning.  The  crown  sheet  of  this 
boiler  is  accessible  from  end  to  end;  an  inspector  can 
crawl  all  over  it,  examine  every  portion,  and  remove  any 
scale  or  dirt  which  may  have  lodged  upon  it.  The  cir- 


STRONG'S  LOCOMOTIVE  FIRE  BOX. 


283 


dilation  of  water  is  entirely  unimpeded;  the  water  un- 
der the  fire  box  is  free  to  rise  without  any  obstruction 
whatever. 

The  inner  shell  has  no  joint  which  is  in  contact  with 
the  fire,  except  that  connecting  the  back  tube  plate  and 
combustion  chamber,  which  does  not  differ  from  common 
practice.  The  life  of  this  boiler,  as  shown  by  actual  ex- 
perience, is  three  to  four  times  that  of  the  ordinary  stayed 


FIG.  62. 


boiler  with  the  same  surface,  proving  that  the  construction 
is  not  only  theoretically  correct,  but  practically  in  advance 
of  boilers  of  the  ordinary  type. 

By  the  system  of  double  furnaces  with  alternate  firing, 
almost  absolute  perfection  in  combustion  is  secured,  with 
total  absence  of  smoke  and  almost  total  absence  of  fire 
from  the  stack,  as  a  very  light  draft  can  be  used,  steaming 
freely  with  2^/2  to  3  inches  of  vacuum,  while  the  ordinary 


284  COMBUSTION    OF   COAL. 

locomotive  would  require   under  the  same  conditions  of 
working  from  8  to  12  inches. 

Q.  How  is  the  smokeless  combustion  of  bituminous  coal 
carried  out  in  practice  ? 

The  smokeless  combustion  of  bituminous  coal  is  being 
very  successfully  carried  out  in  locomotives  on  the  South- 
ern Pacific  Railway,  burning  a  coal  known  as  Castle  Gate, 
mined  in  Utah,  analzying  as  follows  : 

Moisture 2.15  per  cent. 

Volatile  combustible 39. 10       " 

Fixed  carbon 50. 75       " 

Ash 7.40       " 

Sulphur 60       " 

Mr.  J.  Snowden  Bell,  a  locomotive  expert,  made  a  care- 
ful examination  into  all  the  conditions  which  obtain  in  that 
road,  both  as  regards  fire-box  design  and  draft  appliances, 
and  the  method  of  firing.  The  engine  on  which  Mr.  Bell 
made  his  observations  was  a  lO-wheeled  Schenectady,  of 
the  1800  class,  having  20x26  inch  cylinders.  When  rid- 
ing on  the  engine  up  a  io8-foot  grade,  hauling  6  passenger 
coaches,  the  fire  was  kept  clear  and  bright,  without  either 
being  heavy  or  having  holes  in  it;  steam  was  maintained 
at  1 80  pounds,  and  the  fire  door  was  never  closed.  Mr. 
Bell  says  he  never  saw  a  soft- coal  burning  engine,  either 
on  a  level  or  on  a  grade,  which  could  be  compared  as  to 
freedom  from  smoke ;  the  light  and  frequent  firing  which 
was  practised  was,  in  his  opinion,  the  correct  and  intelli- 
gent one,  and  involved  less  fatigue  on  the  fireman  than 
the  ordinary  heavy  firing. 

Mr.  H.  T.  Small,  superintendent  motive  power  of  the 
above  road,  contributes  detail  drawings  of  all  the  mechani- 
cal features  which  contribute  to  this  result,  as  applied  es- 
pecially to  i2-wheel,  22x26  inch  locomotives. 


FRONT  ENDS  OF  LOCOMOTIVES. 


285 


Q.  What  are  the  details  of  the  front  ends  of  locomo- 
tives, Southern  Pacific  Railway  ? 

The  interior  arrangement  of  front  ends,  shown  in  Figs. 
63  and  64,  is  also  practically  the  same  as  recommended 
by  the  Master  Mechanics'  Association  in  1896,  and  is 
giving  satisfactory  results.  It  has  been  adopted  as  stand- 


FlG.  63. 

ard  by  the  Southern  Pacific,  notwithstanding  that  it  is 
necessary  to  use  7x7  mesh  netting,  and  during  the  dry 
summer  months  8x8  mesh  netting  in  engines  running 
through  the  valley  district.  The  exhaust  pipe  and  nozzle 
for  the  twelve-wheeler  class  are  given  in  Fig.  65. 

The  standard  cast-iron  stack  and  saddle  (Fig.  66)  are 
used  on  several  classes  of  engines,  and  the  results  obtained 
in  service  are  entirely  satisfactory.  Although  incorrect  in 
theory,  it  has  been  fully  demonstrated  that  it  is  really  un 


286 


COMBUSTION    OF   COAL. 


FIG.  64. 


these  have  been  used  since 
1890.  It  will  be  noted  that 
the  stack  shown  is  practically 


necessary  to  incur 
the  expense  of 
maintaining  a 
special  pattern  of 
stack  for  each 
class  of  engines, 
and  as  a  matter  of 
fact  the  Southern 
Pacific  has  only 
three  patterns  of 
stacks  for  the  en- 
tire system,  and 


FIG.  65. 


FIG.  66. 


FURNACE    DOOR    FOR    LOCOMOTIVES. 


287 


the  same  as  that  recommended  by  the  Master  Mechanics' 
Association  in  1896. 

Q.  What  are  the  details  of  furnace  door  on  locomotives, 
Southern  Pacific  Railway? 

The  furnace  door  (Fig.  67)  is  used  on  all  coal-burning 
engines,  the  door  proper  being  in  two  sections.  The  up- 
per section,  commonly  called  the  "  trap,"  is  left  open  con- 


FlG.  67. 

tinually  while  the  engine  is  working,  and  through  this 
opening,  which  is  6  x  i  5  inches  for  the  large  engines,  the 
fireman  charges  coal  into  the  fire  box.  It  will  be  noted 
that  the  deflector,  projecting  through  the  door  and  opening 
into  the  fire  box,  is  adjustable  to  any  angle  desired;  it  so 
guides  the  air  admitted  through  the  "  trap  "  as  to  best  aid 
combustion,  and  its  proper  position  is  determined  very 
readily  by  the  enginemen.  It  also  serves  as  a  check  on 


288 


COMBUSTION   OF   COAL. 


firing  with  large  lumps  of  coal,  or  large  amounts  of  coal 
regardless  of  size. 

The  small  fire-door  opening  was  a  novelty  to  Mr.  Bell, 
as  it  will  be  to  others,  but  is  obviously  an  excellent  fea- 
ture, and  this,  with  the  thorough  and  uniform  distribution 
of  air  and  support  of  fuel  by  Mr.  Heintselman's  latest  de- 
sign of  grate,  an  effective  ash  pan,  and  proper  front-end 
arrangements,  are  clearly  the  factors  to  which,  with  good 
firing,  the  results  are  due. 

Q.  What  are  the  details  of  brick  arch  used  in  locomo- 
tives of  Southern  Pacific  Railway? 

The  arrangement  of  the  brick  arch  which  is  of  the  ordi- 
nary type  and  shown  in  Figs.  68  and  69  needs  no  special 


FIG.  68. 


PIG.  69. 


LOCOMOTIVE   GRATE   AND   ASH    PAN.  289 

mention,  excepting  that  it  is  considered  an  important  fac- 
tor, and  helps  to  produce  perfect  combustion  and  economy 
in  fuel  consumption. 

Q.  What  are  the  details  of  grate  used  in  locomotives 
on  Southern  Pacific  Railway? 

The  improved  finger  grates  and  bearings  shown  in  de- 
tail in  Fig.  70  are  novel,  as  is  also  the  manner  of  hanging 
the  grates  from  the  fire-box  sheets.  It  will  be  seen  that 
the  hanging  of  the  side  bars  is  so  arranged  as  to  compen- 
sate for  the  expansion  and  contraction  of  the  grate  bars, 
and  by  means  of  the  collar  at  the  end  of  each  trunnion 
bearing  the  grates  are  held  central  at  all  times,  keeping 
the  air  spaces  equally  divided  between  the  fingers.  The 
air  spaces  through  the  body  of  the  grate  bar  and  fingers 
serve  to  distribute  the  air  to  the  fire  more  evenly,  and  at 
the  same  time  the  thickness  of  the  metal  in  the  body  and 
fingers  is  reduced  to  a  minimum.  The  fingers  being  de- 
tachable, they  can  readily  be  removed  and  replaced  when 
change  of  air  openings  or  spaces  between  fingers  is  desired 
to  suit  different  kinds  of  coal ;  or,  in  case  any  number  of 
fingers  become  damaged  in  any  way  they  can  be  replaced, 
thereby  saving  the  remainder  of  the  grate.  The  fingers 
are  applied  to  the  grate  bars  in  the  rough,  or  just  as  re- 
ceived from  the  foundry. 

Q.  What  are  the  details  of  ash  pan  used  on  locomotives 
of  the  Southern  Pacific  Railway? 

The  general  arrangement  of  the  self-dumping  ash  pan 
(adapted  to  twelve-wheelers)  operated  by  compressed  air  is 
shown  in  Fig.  71,  and  the  application  of  air  valves  to  the 
sides  of  the  ash  pan  is  shown  in  Fig.  72  ;  these  side  valves 
are  also  worked  by  compressed  air.  This  style  of  ash  pan 
is  considered  an  important  improvement,  and  has  resulted 


290 


COMBUSTION    OF   COAL. 


TRAVELLING    FIREMAN.  29 1 

in  a  saving  of  fuel  and  a  saving  in  labor  and  delays  to 
trains  on  account  of  cleaning.  The  side  dampers  distrib- 
ute the  draft  through  the  grates  evenly,  whereas,  in 
former  arrangements  with  only  end  dampers,  the  draft  was 
excessive  through  the  centre  of  the  grate  and  insufficient 
at  the  sides  and  ends.  Clinkers  no  longer  form  on  the 
sides  of  the  fire  box,  and  the  fireman  is  always  free  to 
shake  the  grates,  knowing  that  the  ash  pan  will  not  become 
filled  up,  as  the  new  pans  can  be  dumped  in  a  few  seconds 
by  a  single  movement  of  a  valve.  Therefore  a  light  fire 
can  always  be  carried,  and  there  are  no  delays  for  clean- 
ing. With  former  styles  of  ash  pans  where  the  fireman  re- 
moved the  ashes  with  a  hoe,  trains  were  sometimes  de- 
layed on  this  account  as  long  as  thirty  minutes.  The  new 
ash  pans  are  so  arranged  that  there  is  no  chance  of  sparks 
dropping,  and  when  drifting  down  grades  all  the  dampers, 
if  required,  can  be  closed  with  one  movement  of  the  air 
valve,  or  the  openings  can  be  partially  closed  to  suit  the 
conditions. 

Q.  What  facts  are  given  in  the  daily  report  of  the 
Travelling  Fireman  on  the  Southern  Pacific  Railway? 

One  thing  contributing  to  the  success  of  the  Southern 
Pacific  in  burning  bituminous  coal  is  the  daily  report 
made  by  the  Travelling  Fireman.  This  is  of  value  in 
keeping  the  head  of  the  department  posted  as  to  whether 
the  work  of  firing  is  being  properly  attended  to.  The 
blank  used  for  this  report  gives  the  number  of  the  train, 
date,  names  of  the  enginemen,  and  between  what  stations 
the  report  covers.  The  questions  are  well  designed  to 
bring  out  any  failures  of  the  men  or  machinery,  and  are  as 
follows : 

Kind  of  coal,  and  was  it  broken  to  suitable  size? 


292 


COMBUSTION   OF   COAL. 


DETAILS   OF   ASH    PAN 


293 


294  COMBUSTION    OF   COAL. 

Was  draft  on  fire  properly  equalized ;  if  not,  what  sug- 
gestions have  you  to  offer  ? 

Was  there  any  trouble  due  to  clinkers  or  dirty  fire?  If 
so,  state  cause. 

How  many  times  was  it  necessary  to  clean  fire  over  the 
division  ;  and  time  consumed  in  each  case? 

If  any  trouble  was  experienced  for  want  of  steam,  what, 
in  your  opinion,  was  the  cause  of  it  ? 

What  was  the  condition  of  the  fire  and  ash  pan  on  arrival 
at  terminal  ? 

Was  fireman  disposed  to  comply  with  instructions  and 
practise  economy,  and  prevent  black  smoke  ? 

Was  the  general  condition  of  the  engine  such  that  would 
indicate  any  neglect  whatever  on  the  part  of  the  fireman? 

Was  engine  slipped  unnecessarily? 

Were  injectors  handled  so  as  to  obtain  the  best  results 
in  fuel  economy? 

Was  engine  in  good  serviceable  condition  ?  If  not,  state 
defects. 

The  Travelling  Fireman  is  also  expected  to  note  on  the 
report  or  write  a  letter  regarding  any  other  things  that  may 
be  noticed  while  travelling  or  at  terminals,  that  in  anyway 
would  better  the  engine  service  or  effect  a  saving. 


PART   II. 

HYDROCARBON  OIL   AS    A  FUEL   FOR   LOCO- 
MOTIVES. 

Q.  Is  oil  used  as  fuel  in  locomotives  ? 

It  has  long  been  in  use  in  the  Russian  oil  fields ;  it  has 
been  tested  experimentally  near  the  Pennsylvania  and  Ohio 
oil  fields ;  and  has  been  used  for  fuel  for  several  years  past  on 
the  Pacific  coast.  The  Southern  California  Railroad  began 
burning  oil  in  1894,  and  have  used  it  more  or  less  ever 
since.  Various  minor  changes  have  been  made  with  a 
view  to  improve  the  process ;  but  in  the  main  the  arrange- 
ment has  been  about  the  same  for  the  last  three  or  four 
years ;  and  according  to  Locomotive  Engineering,  about 
all  their  engines  burn  oil  now.  The  Southern  Pacific 
Company  also  burn  oil  in  some  of  their  locomotives.  The 
oil  burners  being  easily  removable,  they  burn  either  oil  or 
coal  according  to  the  relative  prices  of  the  two  fuels. 

Q.  What  advantages  are  claimed  for  petroleum  as  a 
fuel? 

It  is  claimed  for  petroleum  : 

1 .  That  its  heating  power  is  greater  per  pound  than  that 
of  any  solid  fuel. 

2.  That  it  permits  of  continuous  firing  in  a  closed  fur- 
nace, free  from  drafts  of  cold  air. 

3.  That  the  quantity  of  heat  required  to  maintain  a  con- 
stant pressure  of  steam  may  be  controlled  by  the  simple 
adjustment  of  a  valve  in  the  oil-supply  pipe. 


296  COMBUSTION    OF    COAT,. 

4.  Absence  of  debris;  there  being  no  ashes  or  clinkers 
left  in  the  furnace. 

5.  That  the  fire  is  not  only  easily  started,  but  can  be 
instantly  discontinued  without  loss  of  fuel. 

Q.  What  is  petroleum  ? 

Petroleum  is  a  natural  hydrocarbon  oil ;  in  its  widest 
application,  the  term  covers  all  the  mineral  oils  found  in 
this  country.  It  is  of  a  dark-brown  color,  having  a  green- 
ish tinge.  In  specific  gravity  the  crude  oil  averages  about 
0.8,  with  variations  of  .025  on  either  side;  equivalent  to 
50  pounds  per  cubic  foot. 

The  composition  of  crude  oil  is  by  no  means  constant, 
but  it  will  approximate  closely : 

Carbon 84  per  cent. 

Hydrogen 14 

Oxygen 2       " 

100       " 

The  theoretical  heating  power  of  oil  by  this  analysis 
would  be : 

Heat  units. 

Carbon 84  X  14, 544  =  12,217 

Hydrogen  (available) 1375X62,032—    8,529 

Total  heat  units =  20, 746 

The  evaporating  equivalent  of  which  would  be  21.47 
pounds  of  water  from  and  at  212°  F.  per  pound  of  oil. 

Q.  What  is  the  calorific  value  of  petroleum? 

The  heating  power  of  crude  oil  is  greater  than  the  re- 
fined oil,  and  when  employed  as  a  fuel  it  is  the  crude  oil 
that  is  commonly  used  except  locally,  where  the  thick  oily 
residuum  from  the  refineries  is  used  ;  which  is  always  with 
good  effect,  when  the  furnace  details  are  properly  adapted 
for  burning  it. 


HEATING    POWER    OF   OIL.  2Q7 

The  calorific  power  of  crude  oil  approximates  the  fol- 
lowing : 

British 
thermal  units. 

Pennsylvania,  light !7>933 

Ohio,  heavy 18,718 

West  Virginia,  heavy 18, 324 

West  Virginia,  light 18,401 

An  oil  averaging  18,500  heat  units  per  pound  would 
yield  an  equivalent  evaporation  of  19.15  pounds  of  water 
from  and  at  212°  F. 

The  boiler  plant  at  the  World's  Fair,  Chicago,  was  sup- 
plied with  crude  oil  from  the  Lima,  Ohio,  district  for  fuel. 
The  quantity  of  petroleum  used  for  firing  the  main  boiler 
plant  was  upward  of  31,000  tons,  and  the  work  done  was 
stated  to  have  been  32,316,000  horse-power  hours,  or 
about  2.1  pounds  of  oil  per  horse  power  per  hour. 

Q.  What  is  the  calorific  power  of  refined  mineral   oil  ? 

A  commercial  product  known  as  "mineral  seal"  yielded 
upon  analysis : 

Carbon 83. 3  per  cent. 

Hydrogen 13.2       " 

Oxygen,  nitrogen,  and  loss 3.  5       " 


This  oil  has  a  density  of  40°  Baume,  which  corresponds 
to  a  specific  gravity  of  .83.  The  flash  test  was  266°  F., 
and  the  fire  test  311°  F.  It  is  a  pure  mineral  oil.  The 
calculated  heat  units  are : 

British 
thermal  units. 

Carbon 14,500  X  .833  =  12,079 

Hydrogen 52, 370  X  .  132  =    6,913 


18,992 

The  average  result  obtained  by  experiment  is    18,790 


298  COMBUSTION    OF   COAL. 

heat  units,  which  is  i .  i  per  cent  lower  than  the  value  cal- 
culated from  the  analysis  (Jacobus). 

Q.  What  success  has  attended  the  use  of  liquid  fuel  as 
auxiliary  to  coal  for  locomotive  engines? 

Experiments  made  in  England,  on  the  Great  Eastern 
Railway,  have  been  quite  successful  in  the  use  of  liquid 
fuel  as  an  auxiliary  to  coal  in  locomotive  engines.  The 
fluid  used  is  tar,  and  to  it  is  added  a  certain  proportion  of 
green  oil  which  was  also  obtained  from  the  works  where 
the  tar  was  produced,  the  cost  being  about  3  cents  per  gal- 
lon. Each  of  the  12  or  14  engines,  it  appears,  used  about 
1 2  pounds  of  coal  and  over  a  gallon  of  oil,  which  is  equal 
to  about  1 1  pounds  fluid  fuel  per  train  mile  as  against  34 
pounds  of  coal.  The  relative  cost  of  the  combined  mate- 
rial is  rather  less  than  coal,  but  the  value  of  the  oil  injector 
is  seen  to  special  advantage  on  gradients  where  an  extra 
supply  of  steam  is  required. 

Q.  What  success  has  attended  the  burning  of  the  heavy 
residuum  obtained  by  the  distillation  of  bituminous  shale  ? 

Not  much  attention  has  been  given  to  the  distillation  of 
oil  from  bituminous  shale  in  this  country.  Some  lignites, 
for  example  those  found  in  Ouachita  County,  Ark.,  have 
been  experimentally  dealt  with ;  the  lignite  was  soft  enough 
to  be  cut  with  a  knife,  solid,  heavy,  compact,  of  a  bluish- 
brown  color,  disintegrating  by  exposure  to  the  atmosphere. 
It  consisted  of : 

Fixed  carbon  ...    34.  50  per  cent. 

Volatile  matter 60. 50 

Ash 5.00 


100.00 

When  distilled  in  an  iron  crucible,  the  first  product  that 
came  over  was  gas  having  a  feeble  odor  of  sulphurous  acid 


BURNING   OIL   IN    LOCOMOTIVES.  299 

and  burning  with  a  tolerably  bright  flame.  The  gas  was 
soon  accompanied  by  ammoniacal  water,  a  yellowish  oil, 
and  a  waxy  product  which  when  condensed  had  the  con- 
sistency of  lard  and  the  color  of  beeswax.  The  last 
products  which  came  over  were  lubricating  oil  and  par- 
affin. The  products  of  this  distillation  were : 

Coke 37-  83  per  cent. 

Watery  solution  containing  sulphurous  acid,  or- 
ganic acids,  and  ammonia 34-32 

Crude  oil 12.16 

Gas  and  loss 15-69 


100.00       " 

From  this  analysis  2,000  pounds  of  lignite  would  yield 
35.40  gallons  of  crude  oil. 

Crude  residue,  not  unlike  the  above,  left  after  extract- 
ing oil  from  bituminous  shale,  was  applied  for  heating 
purposes  at  the  Forth  bridge.  In  appearance  this  residue 
resembled  butter,  and  would  not  burn  upon  the  application 
of  a  lighted  match.  By  melting  it  and  forcing  it  in  jets 
with  superheated  steam  against  previously  heated  fire-clay 
surfaces  with  an  induced  current  of  air,  it  burned  freely 
and  developed  great  heat. 

Q.  What  changes  are  necessary  to  convert  a  coal  into 
an  oil  burning  locomotive  ? 

To  change  from  coal  to  oil  fuel  on  the  Southern  Califor- 
nia Railroad  the  grates  are  taken  out,  and  a  cast-iron  plate 
is  placed  4  to  6  inches  below  the  mud  ring,  extending 
over  the  entire  space  under  the  fire  box.  This  plate  has 
three  openings  for  air  to  come  up  into  the  fire  box,  9x15 
inches,  one  of  these  air  openings  being  in  the  middle  of 
the  fire  box,  one  near  the  front  end,  and  one  near  the  back 
end.  The  plate  is  protected  from  the  heat  of  the  fire 
above  by  a  covering  of  fire  brick.  The  ash  pan  and  damp- 


300  COMBUSTION    OF    COAL. 

ers  are  left  the  same  as  a  coal  burner.  The  sides  of  the 
fire  box  are  also  protected  from  the  direct  force  of  the  in- 
tense heat  by  a  fire-brick  wall  about  5  inches  thick,  which 
comes  up  to  the  flues  in  front,  up  above  the  flare  of  the 
fire  box  on  the  sides  and  to  the  bottom  of  the  door  at  the 
back.  There  is  a  brick  arch  extending  across  the  fire  box 
from  side  to  side,  reaching  back  pretty  well  toward  the 
door,  just  the  same  as  in  a  soft-coal  burner.  Some  of  the 
engines  also  have  a  narrow  arch  just  under  the  door,  which 
serves  to  keep  the  intense  heat  from  the  door  ring. 

The  atomizer  which  separates  the  oil  into  a  fine  spray 
and  blows  it  into  the  fire  box  is  located  just  under  the 
mud  ring,  pointed  a  little  upward,  so  the  stream  of  oil 
spray  and  steam  would  strike  the  opposite  wall  a  few 
inches  above  the  bottom,  if  it  was  to  fly  clear  across  the 
box.  Deep  fire  boxes  have  the  atomizer  at  the  back  end 
of  the  box,  while  the  shallow  and  long  fire  boxes  have  it 
located  at  the  front  end,  pointed  back.  The  shallow  boxes 
have  the  same  arrangement  of  side  walls  that  the  deep  ones 
have,  but  the  arch  is  put  in  differently.  Some  of  them 
have  three  small  arches  extending  from  side  to  side,  but 
clapping  over  each  other  from  front  to  back,  so  as  to  di- 
vide the  current  of  flame  and  heat  into  several  parts,  and 
thus  distribute  it  over  the  long,  shallow  box  more  evenly. 
A  good  deal  depends  on  the  size  and  position  of  the  arch, 
which  has  the  same  effect  on  the  steaming  of  an  oil  burner 
that  the  diaphragm  in  the  front  end  has  on  the  draft  of  a 
coal  burner.  No  air  is  admitted  above  the  fire  of  the 
atomized  oil. 

Q.  How  are  the  atomizers  constructed  for  burning  oil  on 
the  Southern  California  Railroad? 

The  atomizers,  one  for  each  engine,  are  of  brass,  12 
inches  long,  4)4  inches  wide  from  side  to  side,  and  2 


DETAILS    OF   OIL   BURNER.  301 

inches  thick  from  top  to  bottom,  divided  into  two  parts 
by  a  partition  in  the  middle.  Steam  comes  into  the  bot- 
tom part,  heats  the  atomizer,  and  issues  through  a  slit  •£% 
by  4  inches.  The  oil  flows  into  the  top  part  of  the 
atomizer  over  the  hot  partition,  and  on  running  out  of 
the  front  end  is  caught  by  the  steam  issuing  from  the 
slit  in  the  bottom  part,  and  is  sprayed  into  the  fire,  which, 
when  the  engine  is  working,  is  a  mass  of  flame,  fitting 
the  fire  box  under  the  arch,  and  most  of  the  time  the 
whole  box. 

The  supply  of  steam  and  oil  to  the  atomizer  is  regulated 
by  the  fireman  from  the  cab,  the  handles  for  the  steam  and 
oil  supply  valves  being  placed  where  he  can  have  his  hands 
on  them  when  on  his  seat  box.  Before  the  oil  is  fed  into 
the  atomizer  it  passes  through  a  small  heater  made  of 
brass,  having  a  steam  pipe  through  it ;  this  steam  pipe  also 
leads  to  a  coil  in  the  bottom  of  the  oil  tank  to  warm  the 
oil  so  it  will  flow  easily.  The  oil  on  the  Pacific  coast  is  not 
at  all  like  the  fuel  oil  from  the  Indiana  and  Lima  fields. 
Some  of  the  oil  has  a  generous  portion  of  thick  stuff  like 
asphaltum  in  it,  so  it  does  not  flow  very  easily ;  while  other 
kinds  are  thin  as  water  and  almost  as  clear.  The  oil  tank 
is  located  in  the  pit  of  the  water  tank,  usually  assigned  for 
coal. 

Q.  How  is  the  oil  supplied  to  the  burner  under  pressure  ? 

An  air  pipe  leads  from  the  main  reservoir  to  the  oil 
tank,  with  a  reducing  valve  similar  to  the  one  used  in  the 
air-signal  line,  but  with  a  different  spring  box,  so  as  to 
bring  the  air  pressure  down  to  4  pounds,  which  is  main- 
tained in  the  oil  tank,  at  which  pressure  the  oil  comes  out 
freely.  Self-closing  valves  are  provided  to  shut  off  the 
flow  of  oil  in  case  of  accident. 


302  COMBUSTION    OF    COAL. 

Q.  What  size  of  exhaust  nozzle  is  used  when  burning 
oil? 

It  is  about  the  same  size  as  is  used  when  burning  good 
coal.  Frequently  no  changes  are  made  in  the  front  end 
except  to  take  out  the  netting ;  others  have  a  low  nozzle 
and  petticoat  pipe  put  in  instead  of  high  nozzle  and  a  dia- 
phragm or  apron. 

Q.  Are  oil  fires  smokeless  ? 

An  oil  fire  requires  as  careful  attention  as  does  soft  coal 
to  render  its  combustion  smokeless.  The  fireman  and  en- 
gineer must  work  coincidently  to  get  the  best  results. 
Every  time  the  engineer  changes  his  lever  or  throttle  the 
fireman  must  change  his  fire.  He  must  keep  his  eye  on  the 
water  in  the  boiler,  must  know  the  road,  etc. — in  fact,  a 
good  fireman  on  an  oil-burning  locomotive  must  keep  his 
eyes  open,  for  he  can  make  or  waste  more  for  the  company 
than  he  could  on  a  coal  burner. 

Q.  What  is  the  effect  of  the  products  of  combustion  of 
an  oil  fire  upon  the  tubes  of  the  boiler  ? 

The  products  of  combustion  from  an  oil  fire  make  a 
sticky  deposit  in  the  flues,  which  soon  coats  them  and  in- 
terferes with  the  steaming.  To  cure  this  difficulty,  the 
fireman  sticks  a  long  funnel  through  a  hole  in  the  fire-box 
door,  made  for  that  purpose,  and  gives  the  flues  a  dose  of 
about  four  quarts  of  sand,  which  is  drawn  through  the  flues 
and  scours  them  out. 

Q.  What  is  the  relative  cost  of  oil  and  coal  as  a  fuel  in 
locomotive  practice  ? 

In  California  coal  is  high  priced;  good  coal  at  Los  An- 
geles costs  $6.50  to  $7.50  per  ton;  oil  costs  about  $2  per 
ton  less.  With  coal  at  $4.80  per  ton  it  is  profitable  to 


PRESCOTT'S   OIL   BURNER.  303 

change  a  locomotive  into  an  oil  burner,  with  oil  at  $i  per 
barrel.  Engines  do  not  steam  as  freely  with  coal,  so  they 
cannot  make  as  good  time  or  handle  as  large  a  train  at  as 
high  a  rate  of  speed.  There  is  apparently  no  limit  to  the 
steaming  power  of  an  oil  burner. 

Q.  What  are  the  general  details  of  construction  of  the 
Prescott  burner  for  liquid  hydrocarbons? 

A  locomotive  fire  box  equipped  with  an  oil  burner  by 
George  W.  Prescott  is  shown  in  Fig.  73.  The  fire  box  is 
lined  with  fire  brick,  and  fitted  with  front  and  back  arches 
as  shown.  An  air-supply  pipe  with  damper,  adjustable 
from  the  cab,  is  also  shown.  Fig.  74  is  a  plan  sectional 
view  of  a  double  burner  provided  with  a  central  oil-receiv- 
ing chamber,  also  shown  in  Fig.  75.  This  oil  chamber  is 
located  inside  a  larger  chamber  in  which  water  or  steam 
under  pressure  may  be  used  for  the  purpose  of  raising  or 
lowering  the  temperature  of  the  oil.  The  casing  of  this 
burner  is  rectangular  in  shape,  and  provided  with  exit 
passages,  into  which  the  oil  is  fed  from  the  oil  chamber 
before  passing  into  the  combustion  chamber.  These  exit 
passages  are  irregular  in  shape  or  larger  at  their  induct 
portions  than  at  their  outlets,  so  as  to  contract  the  supply 
of  oil  at  the  outlet,  so  that  when  the  burner  is  tilted  at  an 
angle,  as  indicated  in  Fig.  75,  the  upper  level  of  the  oil 
will  be  above  the  upper  surface  of  the  contact  opening  and 
form  a  trap,  as  it  were,  to  prevent  gas  or  heated  products 
from  flowing  back  into  the  oil  chamber  to  cause  an  explo- 
sion therein. 

The  casing  of  the  burner  at  its  lowest  portion  is  pro- 
vided with  steam  chambers  having  tapered,  slotted  open- 
ings, in  which  are  movably  mounted  tapered  slide  valves. 
The  exit  openings  of  these  chambers,  in  which  these 


304 


COMBUSTION   OF   COAL. 


PRESCOTT'S  OIL  BURNER. 


305 


306  COMBUSTION   OF   COAL. 

"atomizing  valves  "  are  arranged,  are  located  immediately 


under  the  exit  openings  of  the  liquid  hydrocarbons,  and 
the  steam  chamber  is  connected  with  the  source  of  steam 


PRESCOTT'S  OIL  BURNER. 


307 


under  pressure,  so  that  when  the  valves  are  opened  steam 
under  pressure  contacts  with  the  liquid  hydrocarbon  im- 
mediately, atomizes  the  same,  and  drives  it  into  the  fuel 
chamber  with  sufficient  force  to  meet  the  incoming  atmos- 
pheric air  and  promote  combustion. 

The   steam- supply  chamber  in  which   the  valves   are 


FIG.  76. 

located  is  connected  by  means  of  a  pipe  with  the  source 
of  steam  supply,  so  that  steam  under  pressure  may  be  fur- 
nished the  casing  to  atomize  the  oil.  The  steam-supply 
pipe  is  fitted  with  a  drip  valve,  the  parts  of  which  are  so 
arranged  that  when  steam  under  sufficient  pressure  is  fur- 
nished to  the  chamber  the  drip  valve  is  kept  closed ;  but 
as  soon  as  the  pressure  is  lowered  sufficiently,  the  valve  is 
opened  by  means  of  the  tension  spring  and  the  water  of 


308  COMBUSTION   OF   COAL, 

condensation  allowed  to  drip  out  and  empty  the  chamber 
and  the  pipe. 

The  plug  valves  shown  in  Fig.  76  govern  the  supply  of 
oil  to  the  burner,  and  can  be  operated  from  the  cab,  either 
independently  or  simultaneously. 

Each  atomizing  valve  in  the  burner  is  provided  with  a 
stem  that  projects  out  of  the  rear  end  of  the  casing,  and 
further  provided  with  screw  threads,  worm,  and  worm  gear 
for  adjustment. 

The  steam  or  water  chamber  is  provided  with  a  steam 
pipe,  leading  to  the  source  of  supply  for  heating  the  oil ; 
and  another  pipe  connecting  with  the  water  tank,  should 
cooling  instead  of  heating  be  desired. 

As  shown  in  Fig.  73,  the  burner  is  arranged  at  a  slight 
inclination  from  the  horizontal,  so  as  to  provide  a  trap  and 
prevent  back  flow  of  gas  from  entering,  igniting,  and  ex- 
ploding in  the  oil  reservoir. 


CHAPTER  XII. 

CHIMNEYS    AND   MECHANICAL   DRAFT. 

Q.  What  service  does  a  chimney  render  in  connection 
with  a  steam-boiler  furnace? 

It  is  the  means  generally  employed  for  the  purpose  of 
maintaining  a  draft  of  air  through  the  body  of  burning  fuel 
in  the  furnace.  Its  effectiveness  is  due  to  that  quality 
which  it  possesses  of  maintaining  an  unbalanced  pressure 
between  the  interior  or  combustion  chamber  of  the  fur- 
nace and  the  atmospheric  pressure  without. 

Q.  What  is  the  cause  of  draft  in  steam-boiler  furnaces  ? 

Furnace  draft  is  caused  by  the  difference  in  weight  or 
pressure  of  the  column  of  cold  air  outside  of  the  chimney, 
and  the  weight  of  the  column  of  heated  gases  within  it. 
Air  and  gases,  when  heated,  expand  in  volume,  and  be- 
come less  dense  than  for  equal  volumes  at  a  lower  tem- 
perature ;  this  difference  in  density  is  the  draft-producing 
quality  of  heated  gases. 

Q.  How  does  this  unbalanced  pressure  originate  in  a 
chimney,  and  how  is  it  maintained? 

The  unbalanced  pressure  originates  in  the  fact  that  hot 
gases  occupy  a  larger  volume  for  a  given  weight  than  cold 
gases.  As  there  is  no  exit  for  the  hot  gases  generated  in 
the  furnace  except  through  the  chimney,  a  current  is  at 
once  established  in  that  direction.  By  reason  of  the 
height  of  the  chimney  above  the  furnace,  and  the  fact  that 


COMBUSTION   OF   COAL. 


it  is  filled  with  gases  of  higher  temperature,  and  conse- 
quently of  less  density  than  that  of  the  air  outside  of  the 
chimney,  an  upward  current  of  hot  gases  will  be  main- 
tained so  long  as  any  unbalanced  pressure  exists  between 
the  outside  and  inside  of  the  chimney. 

Q.  What  is  the  rate  of  increase  in  volume  for  different 
temperatures  of  gases  escaping  by  the  chimney  ? 

Let  us  suppose  that  1 8  pounds  of  air  pass  through  the 
furnace  per  pound  of  coal ;  we  then  have  18+1  =  19 
pounds  of  gases.  If  the  temperature  of  the  air  flowing 
into  the  furnace  is  68°  F.,  its  voluine  will  be  241  cubic 
feet;  if  the  temperature  of  the  escaping  gases  be  572°  F. , 
the  volume  will  have  been  increased  to  471  cubic  feet,  a 
difference  of  471-^-241  =  1.95  times  increase  in  volume 
of  the  hot  gases  over  that  of  the  cold  air,  a  ratio  approxi- 
mately of  2  to  i. 

TABLE  30. — VOLUME  OF  ESCAPING  GASES  IN  CUBIC   FEET  PER   POUND 
OF  COAL  BURNED.      (Rankine.) 


Temperature. 

POUNDS  OF  AIR  PER  POUND  OF  COAL. 

Twelve  pounds, 
cubic  feet. 

Eighteen  pounds, 
cubic  feet. 

Twenty-four  pounds, 
cubic  feet. 

12°  F 

150 
161 
172 
205 
259 
3M 
S^Q 
479 
588 

697 
906 

225 
241 

258 
307 
389 
471 
553 
7i8 
882 
1,046 
i,359 

300 
322 
344 
409 
519 
628 

738 
957 
1,176 
i,395 
i,  812 

68        

104        

212 

•3Q2 

C72 

7^2 

I    1  12 

I  4.72 

I  832 

2   5OO 

As  the  lighter  gases  are  confined  to  the  chimney  they 
rise  to  the  top  by  reason  of  their  lesser  gravity,  and  within 


AREA    OF    CHIMNEY.  311 

certain  limitations  the  higher  the  chimney  and  the  higher 
the  temperature  of  the  escaping  gases  the  stronger  or 
more  intense  will  be  the  draft. 

Q.  How  is  the  area  of  a  chimney  determined  for  a 
given  boiler  plant? 

This  detail  in  steam  engineering  has  been  practically 
fixed  by  Ishewood's  experiments,  and  further  corroborated 
by  observations  extending  over  many  years,  including  all 
kinds  of  fuel,  and  in  connection  with  almost  every  im- 
maginable  furnace  contrivance,  grates,  etc. 

It  is  a  common  practice  to  make  the  area  of  the  chim- 
ney bear  some  relation  to  the  grate  surface,  although  the 
latter  does  not  bear,  in  practice,  a  fixed  relation  to  the 
boiler- heating  surface;  and  not  always  to  the  quantity  of 
fuel  to  be  burned,  nor  to  the  rate  of  combustion. 

After  a  series  of  elaborate  experiments  Mr.  Ishewood 
fixed  upon  y&  of  the  grate  area  as  being  the  best  propor- 
tion for  draft  area,  and  this  recommendation  holds  good 
for  both  hard  and  soft  coal  at  ordinary  rates  of  combustion. 

In  practice  the  sectional  areas  of  chimneys  will  be  found 
to  vary  between  l  and  ^  of  the  grate  surfaces  to  which 
they  may  be  attached;  the  latter  proportions  being  for 
very  large  plants  and  in  connection  with  unusual  height 
of  chimney. 

The  area  of  chimney  may  be  based  upon  the  quantity  of 
coal  burnt.  Up  to  1,000  horse  power  the  most  satisfactory 
chimneys  are  those  in  which  from  i}4  to  2  square  inches 
of  chimney  area  are  had  for  each  pound  of  coal  burnt  per 
hour.  If,  say,  600  pounds  of  coal  are  supplied  a  steam- 
boiler  furnace  per  hour,  we  have : 

600  x  1-5  =      900  sq.  in.,  or  34  in.  diameter. 
600  X      2  =  1,200       "        "   39  " 


312 


COMBUSTION    OF   COAT.. 


In  which  case  a  36  or  40  inch  chimney  would  probably 
be  selected. 

Q.  How  is  the  height  of  a  chimney  determined  ? 

In  the  larger  cities  the  height  of  a  chimney  is  often 
determined  by  the  height  of  buildings  in  the  immediate 
vicinity;  city  chimneys  are  often,  for  this  reason,  much 
higher  than  necessary  for  the  mere  purpose  of  securing 
proper  draft. 

Where  there  are  no  local  restrictions  governing  the 
height  of  a  chimney,  those  for  small  powers,  say  30  H. 
P.  and  less,  the  height  may  be  50  to  60  feet;  for  100  H. 
P.  the  height  may  be  70  to  90  feet;  and  for  1,000  H.  P. 
150  feet  in  height  will  be  found  ample  for  draft  purposes. 

A  rule  sometimes  met  with  would  fix  the  height  at  25 
times  the  internal  diameter  of  the  chimney ;  this  is  a  good 
rule  for  a  few  sizes,  but  it  will  not  apply  to  all  diameters. 
Small  chimneys  must  have  a  certain  height  to  get  sufficient 
draft  to  burn  the  fuel.  The  height  of  large  chimneys  is  kept 
down  to  reduce  cost  of  construction.  The  following  heights 
come  within  the  range  of  good  practice : 

A  2-foot  chimney 70  feet  high  =  35       diameters. 

3 
4 

5 
6 

7 


Q.  In  estimating  chimney  draft  where  should  the  chim- 
ney measurement  begin  ? 

Draft  properly  begins  at  the  level  where  the  air  passes 
through  the  fire,  and  not  at  the  level  of  the  ground  at  the 
base  of  the  chimney. 


100 

—  25 

.  .  1  20 

—  24 

iqo 

—  21  67 

.  140 

—  2O 

.  ISO 

-  18.75 

INTENSITY    OF   DRAFT.  313 

Q.  What  is  the  best  temperature  for  chimney  draft? 

The  ordinary  limit  of  temperature  for  escaping  gases 
from  steam  boilers  is  approximately  100°  F.  above  the 
temperature  of  the  steam.  If  steam  is  being  generated  at 
100  pounds  pressure  by  gauge,  the  corresponding  temper- 
ature, would  be  338°  -f-  100°  =  438°  F.,  the  lowest  tem- 
perature for  the  escaping  gases.  On  the  other  hand,  the 
maximum  temperature  would  be  about  584°  F.,  because 
at  that  temperature  the  gases  are  about  one-half  the  den- 
sity of  the  atmospheric  air.  The  best  working  temperature 
will  be  found  to  lie  between  these  two  limits. 

Q.  What  is  meant  by  intensity  of  draft? 

Intensity  of  draft  denotes  the  velocity  of  flow  of  air 
through  the  furnace.  Intensity  is  secured  by  height  of 
chimney,  by  high  temperature  of  escaping  gases,  or  both 
combined.  Anthracite  coal  requires  a  greater  intensity  of 
draft  than  is  necessary  for  bituminous  coal,  and  it  is  for 
this  reason  chimneys  for  the  latter  coal  can  be  1 5  to  20 
per  cent  lower  than  for  anthracite.  The  intensity  of 
draft  for  anthracite  coal  will  vary  from  ^  to  I  inch  of 
water ;  for  bituminous  coals,  ^  to  fo  inch  of  water  will 
suffice. 

Q.  How  may  the  intensity  of  chimney  draft  be  esti- 
mated ? 

Intensity  of  chimney  draft  is  usually  measured  in  inches 
of  water.  Suppose  a  chimney  to  be  150  feet  high  and  the 
temperature  of  the  escaping  gases  600°  F.,  the  tempera- 
ture of  the  atmosphere  75°  F.,  the  draft  in  inches  of  water 
may  be  found  thus :  To  the  sensible  temperature  600°  and 
75°  we  must  add  the  absolute  temperature  460°  F.  ;  then : 

460°  +  600°        1 59000 
150  X  460°+    75°  =     535-  =  297  feet ;  297  "  I5°  = 


3X4  COMBUSTION   OF   COAL. 

147  feet,  the  motive  column.     Water  is  820  times  heavier 

than  air,  we    have  then:  =  1656,  which  ex- 

I47 
presses  the  relation  of  weight  as  compared  with  water. 

If  we  divide  the  motive  column  by  this  amount  we  have 

147 
— Pg  =  .0887  foot.     Then  .0887  X  12  =  1.064  inch,  say 

lyL  inches  of  water  by  draft  gauge,  or  the  height  of  a 
column  of  water  lifted  by  the  action  of  a  chimney  corre- 
sponding to  the  height  and  temperature  above  given. 

The  above  example  may  be  regarded  as  an  extreme  case ; 
a  much  lower  set  of  conditions  are  here  given : 

Suppose  a  chimney  100  feet  high,  escaping  gases  500° 
F.,  atmosphere  60°  F.,  what  will  be  the  draft  in  inches 
of  water  ? 

460°  +  500°       96000 
loo  X  \  o        ^  o   =  —     -  =  184  feet. 
460°  -f  60°          520 

184  —  100  =  84  feet.     The  motive  column. 

820  X 
Then:        -^ 

pared  with  water. 


820  X  184 
Then  :  -  =  1 796,  the  ratio  of  weight  as  com- 


84 
Dividing   the    motive    column  by   this  ratio : 


1796 
.0467  foot. 

Then  .0467  X  1 2  —  .560  inch  of  water,  or  about  -f$  inch. 

Q.  Why  is  maximum  economical  chimney  temperature 
taken  to  be  about  584°  F.? 

Chimney  temperature  is  for  draft  purposes  only;  draft 
increases  with  the  temperature  of  the  gases  in  the  chim- 
ney;  from  32°  to  300°  F.the  draft  augments  very  rapidly, 
from  300°  to  750°  the  draft  varies  but  little,  and  then 


PROPORTIONS    FOR   CHIMNEYS.  315 

gradually  diminishes  in  intensity  with  higher  tempera- 
tures. 

An  ordinary  steam  pressure  for  high-grade,  triple-expan- 
sion engine  is  185  pounds  by  gauge,  or  200  pounds  abso- 
lute; the  temperature  of  which  is  382°  F.,  to  which  we 
add  1 00°  for  excess  temperature,  difference  of  hot  gases 
over  that  of  the  steam  —  483°  F. 

The  best  draft  is  had  when  the  density  of  gases  within 
and  without  the  chimney  is  as  2  to  i .  Suppose  an  aver- 
age air  temperature  of  62°  F.,  the  absolute  temperature 
would  be  62°  4- 460°  —  522°;  the  best  draft  would  be 
522°  X  2  =  i, 044°  absolute,  or  1,044°  —  460°  =  584°,  the 
temperature  of  the  gases  in  the  chimney. 

Q.  What  rule  governs  the  proportions  for  chimneys  as 
given  in  Table  31  ? 

Proportions  for  chimneys  from  20  to  90  horse  power  are 
for  a  single  boiler  and  furnace  in  which  the  grate  area  is 
assumed  to  be  9  times  that  of  the  tube  area  for  the  small- 
est horizontal  tubular  boiler,  diminishing  to  7  times  the 
tube  area  for  the  largest  boiler.  A  commercial  horse- 
power rating  approximating  i  5  square  feet  of  heating  sur- 
face per  horse  power  is  assumed  for  all  boilers  included  in 
the  above  grouping. 

For  chimneys  from  100  to  1,000  horse  power,  the  di- 
mensions are  suited  to  two  or  more  boilers  set  in  a  battery 
and  working  together ;  a  horse  power  in  this  portion  of  the 
table  is  based  on  4  pounds  of  coal  per  horse  power  per 
hour. 

The  rate  of  combustion  is  assumed  to  be  12  pounds  per 
square  foot  of  grate  surface  per  hour.  The  proportion  of 
grate  to  chimney  area  varies  from  ^  for  the  100  horse- 
power boiler  to  ^  for  the  1,000  horse-power  boiler. 


COMBUSTION   OF  COAL. 


TABLE  31.— CHIMNEY  DIMENSIONS  FOR  STEAM-BOILER  FURNACES  FROM 
20  TO  1,000  HORSE  POWER. 


HEIGH 

r  FOR  — 

Horse 
power. 

Grate  area, 
square  feet. 

Coal 
per  hour, 
pounds. 

Area 
of  chimney, 
square  feet. 

Diameters 
round 
chimney, 
inches. 

Bituminous 
coal,  free 
burning, 
feet. 

Small 
anthracite 
coal,  feet. 

2O 

12 

2.  02 

20 

50 

60 

30 

14 

.    .... 

2.28 

2O 

55 

65 

40 

17 

.... 

2,gl 

24 

55 

70 

50 

23 

.... 

3.67 

26 

60 

70 

60 

24 

3.80 

27 

60 

75 

70 

29 

4-35 

28 

65 

80 

80 

34 

4.88 

30 

65 

85 

90 

38 

.... 

5.00 

30 

70 

90 

100 

40 

400 

4.76 

30 

70 

90 

150 

50 

600 

6.82 

36 

75 

95 

200 

67 

800 

8.69 

40 

80 

IOO 

250 

83 

,000 

10.64 

44 

85 

105 

300 

100 

,200 

12.50 

48 

85 

105 

350 

117 

,400 

14.18 

51 

90 

1  10 

400 

133 

,600 

16.00 

55 

90 

H5 

450 

150 

,800 

17-65 

57 

90 

H5 

500 

167 

2.OOO 

19-25 

60 

95 

1  20 

550 

183 

2,2OO 

20.65 

62 

95 

120 

600 

200 

2,400 

22.22 

64 

IOO 

125 

650 

217 

2,600 

23.65 

66 

100 

125 

700 

233 

2,800 

25.01 

68 

105 

130 

750 

250 

3,OOO 

26.32 

70 

105 

135 

800 

267 

3,200 

27.6l 

72 

.   no 

135 

850 

283 

3,400 

28.82 

73 

no 

I4O 

900 

300 

3,600 

30.00 

74- 

"5 

145 

95° 

317 

3,800 

31.67 

76 

H5 

.    145 

1,000 

333 

4,000 

33-33 

78 

120 

150 

Q.  How  may  the  draft  of  a  chimney  be  modified  ? 

If  the  chimney  draft  is  sluggish  it  may  be  increased  by 
means  of  a  specially  contrived  blower  exhausting  upward 
in  the  chimney  as  in  Fig.  77.  In  small  boiler  plants,  and 
especially  where  a  sheet-iron  stack  is  employed,  the  ex- 
haust pipe  from  a  non-condensing  engine  is  quite  frequent- 


STEAM    BLOWER. 


317 


ly  led  into  the  stack,  the  pipe  turned  upward,  and  termi- 
nating  in    a    contracted    orifice;    the   size    of  the    latter 
being    usually    determined    by 
local  conditions. 

Excess  of  draft  may  be  con- 
trolled by  means  of  a  damper, 
placed  between  the  exit  of  the 
gases  from  the  boilers,  and  the 
chimney.  In  small  boiler  plants, 
and  especially  those  having  a 
sheet- iron  stack,  the  damper 
is  commonly  placed  either  in 
the'  breeching  or  in  the  stack 
itself. 

Q.  What  is  the  construction  of 
the  argand  steam  blower  ? 

This  blower,  as  made  by 
James  Beggs  &  Co.,  is  shown 
in  section  in  Fig.  78,  and  one 
method  of  applying  it  through 
a  side  wall  of  a  boiler  furnace 
is  shown  in  Fig.  79.  The  blast 
is  regulated  to  suit  the  require- 
ments of  any  furnace  by  means 
of  a  globe  valve  in  the  steam- 
supply  pipe.  Should  the  small 
holes  in  the  argand  ring  become 
clogged  with  loose  scales  from 
the  steam  pipe  or  other  cause, 
they  can  be  cleansed  with  a 
bent  wire  (hook  shaped),  when 
steam  is  turned  on  full  force,  FlG>  77> 


COMBUSTION   OF   COAL. 


FIG.  78. 

Q.  What  is  the  best  location  for   a   steam  blower  in 
connection  with  a  boiler  furnace? 

It  is  generally  conceded  by  those  who  have  given  the 
subject  special  attention  that  a  blast  furnished  by  under- 

grate  combined  air  and  steam 
blowers,  properly  proportioned, 
is  better  adapted  to  burn  the 
smaller  anthracite  fuels  than 
either  a  strong  natural  draft 
or  a  draft  produced  by  a  jet  or 
jets  in  the  stack. 

Both  of  the  latter  methods 
so  relieve  the  pressure  on  the 
upper  surface  of  the  fire  that 
the  unconsumed  gases  escape 
into  the  stack  before  they 
have  time  to  ignite,  whereas 

with  the  forced  draft  a  pressure  is  produced  between  the 
uptake  and  the  upper  surface  of  the  fire  which  retards 
the  gases  long  enough  for  them  to  ignite,  whereby  the 
boiler  can  be  heated  more  effectively  than  by  the  radiant 
heat  alone  which  is  emitted  from  the  incandescent  carbon 
and  radiated  against  a  small  portion  of  the  heating  surface 


FIG. 


79- 


STEAM- JET    BLOWER.  319 

only.  Then,  again,  the  steam  has  a  mechanical  effect,  in 
that  it  keeps  the  clinkers  soft  and  porous,  so  that  the  blast 
will  readily  pass  up  through  the  entire  bed  of  fuel  uni- 
formly, instead  of  being  forced  to  pass  between  solid 
clinkers  wherever  it  can  find  an  opening,  as  is  the  usual 
case  with  a  fan  blast,  for  an  all-air  blast  tends  to  form  the 
clinkers  into  compact  slabs,  through  which  the  air  cannot 
pass. 

Another  mechanical  effect  of  the  steam  is  that  it  mois- 
tens the  fine  ashes  in  the  lower  strata  of  the  fire,  which 
keeps  them  from  being  blown  up  into  the  burning  surface 
to  choke  it  by  filling  the  interstices  between  the  particles 
of  fuel. 

Q.  What  special  preparation  of  fuel  is  recommended  in 
connection  with  a  steam-jet  blower  in  the  ash  pit? 

In  all  cases  where  anthracite  culm  is  used  for  fuel,  it 
should  be  sprinkled  with  water  before  putting  it  on  the 
fire,  not  so  as  to  make  it  sloppy  and  heavy,  but  just  enough 
to  make  the  dust  adhere  to  the  particles  of  small  coal. 
Anthracite  screenings  from  coal  yards  should  be  treated 
in  the  same  manner,  and  if  they  have  lain  out  in  the 
weather  for  any  considerable  length  of  time,  it  will  be 
found  advantageous  to  mix  them  with  about  one-fifth  their 
bulk  of  bituminous  slack,  where  it  is  available. 

A  very  simple  yet  very  important  feature  in  burning 
fine  fuels  successfully,  where  the  argand  blowers  are  used 
to  furnish  blast,  is  to  close  the  damper  in  the  chimney,  or 
stack,  to  a  point  where  the  burning  gases  will  not  blow  out 
through  the  fire  door  when  opened,  for  where  there  is  a 
strong  chimney  or  stack  draft  in  connection  with  the  under- 
grate  blowers  a  large  percentage  of  the  gases  escape  with- 
out igniting.  Therefore  one  should  not  fail  to  so  regulate 


320  COMBUSTION   OF   COAL. 

the  damper  that  the  largest  possible  volume  of  gaseous 
flame  may  be  produced  in  the  furnace.  Where  the  chim- 
ney draft  is  weak,  it  may  be  necessary  to  keep  the  damper 
wide  open,  but  it  has  been  found  that  in  the  majority  of  cases 
it  is  not  only  beneficial,  but  absolutely  essential,  to  regu- 
late the  dampers  as  described  in  order  to  produce  the  best 
results. 

Q.  What  is  mechanical  draft  ? 

This  name  is  commonly  applied  to  any  system  of  press- 
ure or  exhaust  fans  driven  by  a  separate  mechanism,  by 
which,  in  the  case  of  a  blower,  a  current  of  air  is  forced 
through  the  fire ;  or  by  exhaustion  of  the  products  of  com- 
bustion by  means  of  a  vacuum  created  by  a  revolving  fan* 
placed  beyond  the  uptake  or  in  the  breeching  leading  to 
the  chimney.  In  either  case  the  air  needed  for  combus- 
tion is  supplied  the  fire  through  mechanical  means  and 
not  by  natural  draft. 

Q.  What  are  the  ordinary  methods  of  application  of 
mechanical  draft  ? 

The  commonest  method  is  by  means  of  a  centrifugal 
fan,  or  fan  blower,  by  means  of  which  the  air  needed  for 
combustion  is  forced  through  the  fire.  The  air  supply  in 
stationary  boiler  practice  is  usually  forced  into  an  air- 
tight ash  pit,  and  as  there  is  no  other  escape  for  the  air  it 
is  forced  through  the  fuel,  and  thus  becomes  a  "forced" 
draft.  Another  method,  frequently  employed  on  steam- 
ships, is  to  make  the  fire-room  air  tight  and  force  the  air 
into  it  at  such  pressure  and  in  such  volume  as  may  be 
needed  for  the  combustion  of  the  fuel. 

A  typical  arrangement  of  the  B.  F.  Sturtevant  Com- 
pany's steam  fan  for  the  production  of  under- grate-forced 
draft  is  shown  in  Fig.  80.  The  fan  discharges  the  air 


322 


COMBUSTION   OF   COAL. 


into  an  underground-brick  duct  extending  along  the  front 
of  the  battery  of  boilers.  From  this  duct  smaller 
branches,  two  to  each  boiler,  extend  to  the  ash  pits,  to 
which  the  air  is  admitted  in  the  requisite  amount  through 
ash-pit  dampers  of  the  type  shown  in  Fig.  81.  There  is 


FIG.  81. 


thus  maintained  within  the  ducts  and  ash  pits  a  pressure 
greater  than  that  of  the  atmosphere  by  an  amount  depend- 
ent upon  the  speed  of  the  fan,  which  may  be  regulated  at 
will. 

Q.  What  objections  are  there  to  the  closed  ash-pit 
system  ? 

An  objection  to  the  direct  introduction  of  air  under  press- 
ure by  means  of  'a  pipe  in  the  bottom  of  or  through  one 
side  of  a  closed  ash  pit,  is  found  in  the  failure  properly  to 


MECHANICAL   DRAFT. 


323 


distribute  the  air  in 
the  ash  pit  (see  Fig. 
82),  resulting  in  un- 
equal combustion,  lo- 
calizing the  heat  in 
certain  portions  of 
the  grate,  and  pro- 
ducing blow-holes  in 
others. 

The  air  pressure  in 
the  ash  pit,  being  in 
excess  of  that  of  the 
atmosphere,  necessi- 
tates keeping  the  ash- 
pit doors  closed ;  this 
pressure  also  causes 
all  leakage  to  be  out- 
ward. The  tendency 
is,  therefore,  to  blow 

the  ashes  out  of  the  ash  pit,  and  the  flame,  smoke,  and 
fuel  out  of  the  fire  doors. 

Q.  How  may  the  objections  to  the  closed  ash-pit  system 
be  overcome? 

So  far  as  the  localization  of  the  combustion  is  concerned 
it  may  be  overcome  by  deflecting  the  air  entering  the  ash 
pit  by  means  of  a  damper  as  shown  in  Fig.  83.  This  de- 
vice, by  the  B.  F.  Sturtevant  Company,  insures  a  thorough 
distribution  of  the  air  throughout  the  ash  pit  before  it  rises 
to  the  grate.  The  air  duct  is  in  this  case  constructed  with- 
in the  bridge  wall,  there  being  one  or  more  dampers  for 
each  boiler.  The  amount  of  opening  is  regulated  by  the 
handle  shown  in  the  engraving. 


FIG.  82. 


324 


COMBUSTION    OF   COAL. 


A  hollow-blast  grate  is  one  of  the  devices  for  equably 
distributing  the  air  and  stimulating  draft  in  connection 


FIG.  83. 

with    mechanical    draft  apparatus.     The  Gordon    hollow- 
blast   grates    in   combination   with  a  Sturtevant   fan    are 


FIG.  84. 


shown  in  Fig.  84.      The  grate  bars  are  cast  hollow,  and 
have  suitable  openings  adapted  for  burning  coal,  coal  ref- 


INDUCED    DRAFT.  325 

use,  bagasse,  tanbark,  etc.  The  main  blast  pipe  enters 
the  ash  pit  through  one  of  the  side  walls;  suitable  tubes 
connect  the  blast  pipe,  and  the  grate  bars  above,  thus  es- 
tablishing an  air  connection  between  the  two. 

Q.  What  is  the  induced  system  of  draft? 

The  induced  suction  or  vacuum  method  for  obtaining 
a  suitable  draft  for  furnace  combustion  consists  in  the  in- 
troduction of  an  exhausting  fan  in  the  place  of  a  chimney. 
The  fan  serves  to  maintain  the  vacuum  which  would  exist 
if  a  chimney  were  employed,  and  its  capacity  can  be  made 
such  as  to  handle  the  gases  which  result  from  the  proc- 
esses of  combustion.  As  the  draft  is  thus  rendered  prac- 
tically independent  of  all  conditions  except  the  speed  of 
the  fan,  it  is  necessary  to  provide  only  a  short  outlet  pipe 
to  carry  the  gases  to  a  sufficient  height  to  permit  of  their 
harmless  discharge  to  the  atmosphere.  In  practice  the 
capacity  of  an  induced  draft  fan,  as  measured  by  the 
weight  of  air  or  gases  moved,  necessarily  varies  with  the 
temperature  of  the  gases  it  is  designed  to  handle.  There- 
fore the  density,  which  varies  inversely  as  the  absolute 
temperature,  should  enter  as  a  factor  in  all  such  calcula- 
tions. The  simplest  arrangement  for  an  ordinary  boiler 
plant  consists  in  placing  the  fan  immediately  above  the 
boiler,  leading  the  smoke  flue  directly  to  the  fan-inlet 
connection,  and  discharging  the  gases  upward  through  a 
short  pipe  extending  just  above  the  boiler-house  roof. 

The  induced  draft  system  is,  on  the  whole,  better  sub- 
ject to  control  than  the  other  systems;  its  leakage  is 
always  inward,  avoiding  inconvenience  from  flame  and 
smoke  at  the  fire  doors,  it  lends  itself  readily  to  control 
by  the  dampers  which  may  be  introduced  for  the  pur- 
pose. 


326  COMBUSTION   OF   COAL. 

An  induced-draft  plant  is  shown  in  Fig.  85,  consisting 
of  4  Manning  boilers,  each  boiler  containing  180  tubes 
2y2  inches  in  diameter,  15  feet  long;  fire  box  6  feet  in 
diameter,  28,27  square  feet  of  grate  surface,  and  1,823 
square  feet  of  total  heating  surface  for  each  boiler.  The 
economizer  contains  192  tubes,  4^  inches  in  diameter; 
the  square  feet  of  heating  surface  is  2,304.  The  two 
Sturtevant  fans  have  a  somewhat  novel  arrangement, 
whereby  a  relay  Is  provided  and  the  floor  area  occupied  is 
reduced  to  a  mimimum.  Each  fan  has  a  wheel  7  feet  in 
diameter,  and  driven  by  direct-connected  engine.  By 
means  of  an  arrangement  of  dampers,  the  gases  may  be 
caused  to  pass  through  the  economizer,  and  thence  to 
either  one  or  both  fans,  whence  they  are  discharged 
through  a  short,  vertical  stack.  The  experimental  results 
obtained  furnish  an  interesting  commentary  upon  the  re- 
lations between  fan  speed,  volume  moved,  pressure  cre- 
ated, and  horse  power  required.  Up  to  a  certain  speed 
the  natural  draft  of  the  short  stack  is  equal  to,  or  actually 
exceeds,  that  created  by  the  operation  of  the  fans;  but 
when  the  draft  produced  by  the  fans  exceeds  that  which 
the  stack  is  capable  of  creating,  the  additional  work  is 
thrown  upon  the  fans,  and  the  power  increases  practically 
as  the  cube  of  the  number  of  revolutions. 

Q.  What  is  the  proper  kind  of  fan  for  use  in  connec- 
tion with  a  mechanical  draft  apparatus  ? 

Two  types  of  fans  exist.  The  first,  known  as  the  disc 
or  propeller  wheel,  is  constructed  on  the  order  of  a  screw 
propeller,  and  moves  the  air  in  lines  parallel  to  its  axis, 
the  blades  acting  on  the  principle  of  the  inclined  plane. 
The  second,  or  fan  blower  proper,  consists  in  its  simplest 
form  of  a  number  of  blades  extending  radially  from  the 


n-nr 


328  COMBUSTION    OF    COAL. 

\ 

axis,  and  presenting  practically  flat  surfaces  to  the  air  as 
they  revolve.  By  the  action  of  the  wheel  the  air  is  drawn 
in  axially  at  the  centre  and  delivered  from  the  tips  of  the 
blades  in  a  tangential  direction.  This  type  may  be  sim- 
ply designated  as  the  centrifugal  fan,  or,  more  properly,  as 
the  peripheral  discharge  fan. 

The  propeller  or  disc  fan  is  practically  useless  as  a 
means  of  draft  production.  The  desired  results  can  be 
secured  only  by  the  use  of  the  peripheral  discharge  type. 

Theoretically  there  should  be  a  difference  in  the  form 
of  wheels  designed  for  creating  pressure  and  creating  a 
vacuum ;  practically  the  distinction  between  a  blower  and 
an  exhauster  is  one  of  adaptation  rather  than  of  construc- 
tion. 

Q.  What  are  the  advantages  claimed  for  mechanical 
draft? 

The  advantages  claimed  may  be  summarized,  for  land 
requirements  as  distinguished  from  marine,  in  that  by  its 
introduction  greater  economy  in  the  first  cost  or  running 
expense  of  a  steam  plant  may  be  secured. 

As  compared  with  chimney  draft,  a  chimney  requires 
certain  fixed  and  practically  unalterable  conditions  for  its 
location  and  erection,  and  is  only  to  a  limited  extent 
adaptable  to  changes  in  its  requirements.  Mechanical 
draft  apparatus  may,  on  the  contrary,  be  adapted  to  a  great 
variety  of  conditions,  such  as  accommodation  to  restricted 
space;  or  it  may  be  placed  in  any  convenient  location 
and  not  necessarily  in  the  fire  or  engine  rooms. 

Perfect  control  may  always  be  maintained  over  the  action 
of  mechanical  draft.  With  a  chimney  the  intensity  of  the 
draft  is  least  when  the  fire  is  low ;  with  the  fan  it  is  pos- 
sible instantly  to  produce  the  maximum  draft  under  these 
conditions. 


MECHANICAL   DRAFT.  329 

Climatic  conditions  do  not  affect  mechanical  draft;  it 
can  be  made  as  strong  in  summer  as  in  winter,  and  on  a 
muggy  day  as  on  one  that  is  bright  and  clear. 

Increased  rates  of  combustion  are  readily  had  by  means 
of  mechanical  draft,  and  the  capacity  of  a  boiler  largely 
increased  at  any  time  to  suit  temporary  or  permanent  con- 
ditions. 

The  burning  of  cheap  and  low-grade  fuels  is  best  ac- 
complished by  means  of  a  mechanical  draft. 

The  prevention  of  smoke,  usually  a  mere  incident  to  the 
application  of  mechanical  draft,  has  sometimes  been  a 
purpose  sufficient  in  itself  to  warrant  its  installation,  not 
that  a  direct  saving  in  cost  of  fuel  is  had,  but  that  cheap 
and  low-grade  fuels  may  be  used  in  localities  where  smoke- 
prevention  laws  are  enforced.  This  is  on  the  assumption 
that  the  furnace  is  properly  designed,  and  the  introduction 
of  a  fan  blast  merely  insures  rapid  combustion. 

The  utilization  of  waste  heat  in  gases  by  the  use  of  an 
economizer  is  practicable  only  in  the  case  of  a  chimney 
when  the  escaping  gases  are  of  a  comparatively  high  tem- 
perature. When  the  draft  is  produced  by  a  fan,  the  draft 
is  independent  of  the  temperature  of  the  gases,  the  condi- 
tions then  are  favorable  for  utilizing  the  heat  which  is  un- 
avoidably lost  in  the  case  of  a  chimney.  The  saving  in 
fuel  which  may  be  accomplished  under  working  conditions 
by  the  combined  use  of  mechanical  draft  and  economizer 
has  been  experimentally  shown  to  range  between  10  and 
20  per  cent. 


CHAPTER  XIII. 

SPONTANEOUS   COMBUSTION. 

Q.  What  is  meant  by  spontaneous  combustion  ? 

Spontaneous  combustion  means  self-ignition ;  it  is  a 
name  given  to  fires  which  have  their  origin  in  the  heat 
generated  by  chemical  action,  or  by  the  rapid  oxidation  of 
the  substances  thus  ignited.  The  spontaneous  combus- 
tion of  coal  is  due  to  the  chemical  action  set  up  between 
the  carbon  constituents  and  the  atmospheric  oxygen  which 
is  absorbed  by  coal ;  the  volume  of  oxygen  so  absorbed  de- 
pends upon  the  surface  exposed  and  the  porosity  of  the 
coal;  the  chemical  action  evolves  heat,  and  when  this  heat 
is  confined  it  results  in  a  constantly  increasing  tempera- 
ture, and  this  accelerates  the  process  of  oxidation. 

Q.  What  is  the  probable  action  set  up  in  spontaneous 
combustion  between  the  coal  and  the  oxygen  of  the  at- 
mosphere ? 

The  surface  of  each  particle  of  coal  is  active  in  attract- 
ing and  condensing  the  atmospheric  oxygen,  and  the  oxygen 
so  absorbed  is  largely  rid  of  the  dilutent  nitrogen  and,  there- 
fore, is  better  fitted  for  the  process  of  oxidation  which  be- 
gins slowly,  but  at  once.  In  this  process  two  actions  are 
set  up  :  first  the  combination  of  oxygen  with  what  is  called 
the  disposable  hydrogen  in  the  coal  to  form  water;  sec- 
ondly, the  combination  of  oxygen  with  the  carbon,  forming 
carbonic  acid  gas,  and  heat  is  evolved  as  the  result  of  both 


SPONTANEOUS    COMBUSTION.  33! 

actions.  In  the  initial  stage  it  is  not  sensible,  nor  is  it 
apparent  as  in  the  case  of  iron,  where  visible  rust  indicates 
the  process.  When  this  heat  is  subjected  to  the  cooling 
effect  of  the  atmosphere,  or  when  it  can  be  conducted  from 
its  source,  no  danger  is  to  be  apprehended ;  but  where  the 
evolved  heat  is  not  so  conducted  or  cooled,  as  in  the  case 
of  a  mass  of  fine  coal,  the  temperature  will  rise  and  con- 
tinue with  accelerated  rapidity  as  the  ignition  point  is  ap- 
proached (Howard). 

Q.  How  much  oxygen  will  coal  absorb  ? 

It  has  been  experimentally  determined  that  certain 
English  coals  absorbed  twice  their  own  volume  of  oxygen, 
and  in  a  pulverized  state  this  absorption  equalled  2  per  cent 
of  its  own  weight. 

Q.  What  is  Richter's  theory  regarding  the  spontaneous 
combustion  of  coal? 

The  theory  worked  out  by  Richter  is  that  two  of  the 
constituent  elements  of  bituminous  coal,  viz.,  the  carbon 
and  the  hydrocarbons,  have  a  strong  attraction  for  atmos- 
pheric oxygen,  and  under  ordinary  conditions  this  absorp- 
tion of  oxygen  will  be  in  proportion  to  the  surface  exposed, 
to  the  porosity  of  the  coal,  and  to  the  temperature  of  the 
mass. 

Q.  Have  experiments  been  made  to  prove  the  correct- 
ness of  Richter 's  theory? 

The  absorption  of  oxygen  by,  and  chemical  combination 
with,  pulverized  bituminous  coal  is  known  to  occur,  and 
approximately  under  the  following  conditions : 

At  a  low  temperature  the  action  is  slow ;  but  it  rapidly 
increased  when  100°  F.  was  exceeded.  Powdered  coal 
has  been  known  to  fire  in  a  few  hours  at  a  steady  tempera- 


332  COMBUSTION   OF  COAL. 

ture  of  250°  F.  Under  ordinary  conditions,  however,  the 
absorption  was  in  proportion  to  the  surface  exposed,  to  the 
porosity  of  the  coal,  and  to  its  temperature. 

Q.  To  what  element  in  the  coal  is  spontaneous  com- 
bustion generally  attributed  ? 

Sulphur  was  once  believed  to  be  the  real  cause  of  spon- 
taneous combustion  in  coal,  for  the  reason,  probably,  that 
if  it  is  present  in  the  coal  it  is  in  the  form  of  pyrites,  and 
this  was  associated  with  a  well-known  fact  that  heaped-up 
pyrites  in  shale,  when  wetted,  often  cause  the  combustion 
of  the  pile.  The  sulphur  theory  received  the  support  of 
the  noted  Swedish  chemist  Berzelius. 

Q.  What  are  the  objections  to  the  sulphur  theory  in 
the  spontaneous  combustion  of  coal  ? 

It  is  objected  to  because  it  does  not  account  for  the 
numerous  cases  of  the  spontaneous  combustion  of  coal  in 
which  sulphur  is  not  present.  The  investigations  of  Dr. 
Percy  in  England  and  of  Dr.  Richter  in  Germany  showed 
that  the  sulphur  theory  did  not  account  for  all  the  dis- 
covered facts. 

Coals  almost  free  from  sulphur  have  been  observed  to 
be  dangerous,  and  others  heavily  charged  with  it  compara- 
tively safe.  Further  the  sulphur  theory  does  not  account 
for  the  ignition  of  charcoal,  or  of  oily  waste,  nor  of  wool 
when  saturated  with  animal  or  vegetable  oils  and  sub- 
jected to  favoring  temperatures. 

Iron  pyrites,  or  disulphide  of  iron,  is  the  only  sulphur 
compound  found  in  coal  which  by  oxidizing  under  favor- 
able conditions  will  gradually  develop  heat  sufficient  to 
make  self-ignition  a  possibility.  Sometimes,  however, 
the  pyrites  will  rapidly  oxidize,  and  at  others  it  will  re- 


SPONTANEOUS    COMBUSTION.  333 

main  unchanged  for  a  long  period.  The  recent  conclu- 
sions seem  to  point  out  that  pyrite  is  merely  accessory  to 
the  trouble,  in  that  through  oxidation  it  lowers  the  point 
of  ignition  in  the  surrounding  mass  of  coal,  and  in  the 
process  it  swells,  causing  disintegration  of  the  lumps,  and 
consequently  increases  the  absorbing  surface  of  the  coal. 
The  temperature  of  ignition  of  sulphur  is  482°  F.,  whereas 
coal  requires  from  700°  to  900°  F. 

Q.  Can  the  safety  of  coals  as  regards  spontaneous  com- 
bustion be  determined  by  analysis? 

The  difference  between  safe  and  unsafe  coals  cannot  be 
determined  by  proximate  or  ultimate  analysis.  It  is  the 
deep  mass  of  small  and  fine  coal  that  constitutes  the  dan- 
ger ;  and  coals  of  a  firing  tendency  are  dangerous,  some  at 
one  depth  of  pile  and  some  at  another. 

Q.  How  does  carbon  spontaneously  ignite  ? 

Carbon  in  a  finely  divided  state  has  the  power  of  con- 
densing oxygen  within  its  pores ;  now,  to  condense  a  gas, 
force  is  consumed  and  heat  is  produced.  In  the  fire 
syringe,  a  piece  of  tinder  is  set  on  fire  by  the  heat 
evolved  by  the  condensation  of  the  air.  When  charcoal 
condenses  oxygen  heat  is  liberated,  and,  if  the  charcoal  is 
freshly  burned,  the  rapidity  of  the  action  will  produce 
such  an  amount  of  heat  as  to  cause  the  chemical  combina- 
tion of  the  oxygen  and  carbon,  when,  of  course,  combus- 
tion takes  place  with  evolution  of  light  and  heat.  The 
initial  temperature  of  the  action  is  here  due  to  the  sudden 
squeezing  together  of  the  gaseous  molecules,  for  if  the  air 
be  admitted  to  the  freshly  burned  charcoal  by  slow  degrees 
no  combustion  takes  place. 


334  COMBUSTION    OF   COAL. 

Q.  Is  wood  liable  to  spontaneous  combustion  when  placed 
against  or  in  close  proximity  to  hot  surfaces  ? 

The  fact  that  a  hot  steam  pipe  will  char  and  eventually 
ignite  wood  is  well  known  to  fire-insurance  inspectors. 
The  application  of  moderate  heat  to  wood  dries  up  its 
juices,  renders  it  brittle,  and  ultimately  causes  its  com- 
plete disintegration  and  combustion  if  air  is  supplied, 
though  the  process  is  exceedingly  slow.  At  the  ordinary 
temperature  of  the  air,  oxygen  has  so  little  action  upon 
wood  that  it  is  practically  indestructible. 

Q.  How  should  permanent  woodwork  passing  through 
large  masses  of  bituminous  coal  be  protected? 

By  covering  the  woodwork  with  sheet  iron  well  painted 
to  protect  it,  as  iron  also  suffers  from  oxidation. 

Q.  Does  the  presence  of  wood  in  a  pile  of  coal  affect 
favorably  or  otherwise  the  conditions  leading  to  the 
spontaneous  combustion  of  coal  ? 

It  is  a  well-established  fact  that  the  presence  of  wood 
in  a  pile  of  coal,  whether  present  as  loose  chips  or  as 
forming  supports,  contributes  materially  to  the  fire  risk. 
The  surfaces  of  the  wood  through  a  process  analogous  to 
dry  distillation  become  charred  and  converted  into  char- 
coal or  tinder.  The  tendency  to  oxidation  which  carbon 
and  carbon  compounds,  existing  in  such  a  substance  as 
charcoal,  possess,  is  favored  by  the  condensation  of  oxygen 
within  its  pores,  whereby  the  intimate  contact  between 
the  carbon  and  oxygen  particles  is  promoted.  Hence  the 
development  of  heat  and  the  establishment  of  oxidation 
occur  simultaneously,  the  latter  is  accelerated  as  the  heat 
accumulates,  and  chemical  action  is  thus  promoted,  and 
may,  in  course  of  time,  proceed  so  energetically  that  the 


SPONTANEOUS   COMBUSTION.  335 

carbon  or  carbo- hydrogen  particles  may  be   heated  to  the 
igniting  point. 

Q.  Does  the  height  of  a  pile  of  coal  contribute  to  spon- 
taneous combustion? 

The  higher  the  pile  of  coal  the  greater  is  the  fire  risk, 
especially  if  the  coal  is  very  fine.  It  is  a  matter  of  gen- 
eral observation  that  when  fires  break  out  on  shipboard, 
they  originate  directly  under  the  main  hatchways,  or  under 
the  coaling  chutes,  or  in  the  middle  or  near  the  bottom 
of  a  deep  cargo. 

Q.  Is  coal  liable  to  spontaneous  combustion  when  placed 
against  or  over  hot  surfaces? 

So  long  ago  as  1852  Graham  pointed  out  that  the  ten- 
dency of  coals  to  spontaneous  ignition  is  increased  by  a 
moderate  heat.  In  one  case  coal  had  taken  fire  by  being 
heaped  for  a  length  of  time  against  a  heated  wall,  the  tem- 
perature of  which  could  be  easily  borne  by  the  hand.  In 
another,  coal  ignited  spontaneously  after  remaining  for  a 
few  days  upon  stone  flags  covering  a  flue,  of  which  the 
temperature  never  rose  beyond  150°  F.  Examples  are 
sufficiently  numerous  to  fully  establish  the  fact  that 
masses  of  coal  exposed  to  even  a  moderate  heat  become 
hazardous  as  a  fire  risk. 

Q.  Will  small  bodies  of  coal  ignite  spontaneously  ? 

Coal  in  small  quantity  and  in  a  cool  place  never  ignites 
spontaneously;  it  does  not,  therefore,  follow  that  all  the 
conditions  leading  up  to  spontaneous  combustion  are  absent, 
only  that  one  of  them,  and  that  an  all-important  one,  the 
means  of  accumulating  heat,  is  absent,  since  the  barriers 
interposed  to  its  escape  are  not  sufficiently  close-fitting, 


COMBUSTION   OF  COAL. 

Q.  What  would  be  the  effect  of  forcing  air  into  a  body 
of  coal  as  a  means  of  preventing  spontaneous  combustion 
by  forced  ventilation  ? 

When  air  is  forced  into  a  body  of  coal  more  or  less 
oxidation  occurs,  followed  by  a  rise  in  temperature,  the 
heat .  present  or  liberated  by  its  increased  oxidation  is  ab- 
sorbed by  the  coal,  fresh  supplies  of  air  being  continually 
forced  in,  passes  over  and  around  the  oxidizing  surfaces 
of  the  coal  becoming  hotter  and  hotter,  the  air  itself  be- 
comes heated,  and  all  the  conditions  for  combustion  ob- 
tain, which,  if  once  begun,  continue  more  and  more  rapidly 
with  each  increment  of  air  supply. 

Q.  Is  wet  coal  more  liable  to  spontaneous  combustion 
than  dry  coal? 

Water  does  not  assist  in  the  spontaneous  combustion  of 
coal  except  where  pyrites  are  concerned.  There  is  much 
misunderstanding  as  to  the  part  played  by  water  in  the 
changes  leading  to  spontaneous  combustion.  The  water 
itself  is  not  decomposed,  as  some  have  imagined.  The 
heat  evolved  during  the  combustion  of  hydrogen  and 
oxygen  to  form  water  (62,000  heat  units)  must  be  sup- 
plied before  they  can  be  again  torn  apart,  so  that  so  far 
from  water  being  a  producer  of  heat,  it  is  likely  to  be  a 
consumer. 


INDEX. 


ABSOLUTE  zero,  54 
Affinity,  62 

Air,  advantages  of  heated,  88 
ammonia  in,  73 
and  steam  jets  for  locomo- 
tives, 129 

carbonic  acid  in,  73 
composition  of,  68 
conversion    of    pounds    into 

cubic  feet,  77 
density  and  passage  of  heat, 

78 
economical  limit  to  heating, 

90 

effect  of  pre-heating,  79 
surplus,  107 
too  little,  87 
too  much,  88 

excess  of,  in  combustion,  82 
expansion    of,   by    heat,   78, 

151 
heated  and  chemical  action, 

89 
physical    and    chemical 

effects,  80 
heating  and  cooling  of,  77 

coils  for  locomotives,  129 
increase  in  bulk  by  heat,  155 
liquefaction  of,  82 
measuring  flow  of,  101 
non-admission    of,   over    oil 
fires,  300 
22 


Air   not   a  chemical   compound, 
68 

ozone  in,  74 

physical  effects  of  heat  upon, 
78 

pre-heated,  objections  to,  79 

quantity  required    for  com- 
bustion, 8 1 
per  pound  of  coal,  82 

specific  heat  of,  82,  143,  152 

vapor  in,  74 

weight  of,  75 

Allen  and  Tibbitts  furnace  feed- 
er, 245 

Alumina  in  ashes,  114 
American  stoker,  235 
Analysis,  elementary,  160 

proximate,  172 

qualitative,  160 
Anemometer,  102 
Anthracite  coal,  13 

air  required  for,  108 

ashes  from,  109 

classification  of,  13 

composition  of,  14 

physical  properties  of,  n 

small  sizes,  14 

Anthracite  fire,  cleaning  of,  240 
Arch,  brick,  endurance  of,  262 

Murphy's,  124 

oil-burning  locomotives,  300 

Prescott's  oil  burner,  303 


338 


INDEX. 


Area  of  chimney,  311 
Argand  steam  blower,  317 
Arkansas  lignite,  33 
Arndt,  Max,  econometer,   132 
Artificial  fuel,  advantages  of,  44 
Ash-forming  constituents  in  coal, 

12 
Ashes,  alumina  in,  114 

Berthier's  analysis,  117 

color  of,  no 

composition  of,  109 

definition  of  term,  108 

from  lignites,  34 

fusing  of,  in 

iron  pyrites  in,  112 

lime  present  in,  117 

oxide  of  iron  in,  112 

potash  in,  116 

quantity    after   combustion, 
118 

silica  in,  115 

specific  heat  of,  109 
Ash-pit  damper,  322 

system  of  forced  draft,  322 
Ash  pan  operated  by  compressed 
air,  289 

Southern    Pacific    Railway, 
289 

when  to  be  examined,  126 

with  side  valves,  291 
Atmosphere,  68 

density  and  height,  76 

pressure  of,  75 
Atom,  58 
Atomic  value  in  compounds,  65 

weight,  58 

and  specific  heat,  152 
and   symbolic  notation, 

61 

Atomizers  for  burning  oil,  300 
Attraction,  chemical,  63 


Available   heat   of    combustipi, . 

213 
Ayers  and  Ranger,  stoker,  231 

BABCOCK  &  WILCOX  Co.,  quoted, 
207 

stoker,  226 

Baffle  plates  in  locomotives,  279 
Bagasse,  36 

Fisher's  furnace  for,  241 
Barnes'  locomotive  boiler,  266 
Barometer,  76 

Barrus,  G.  H.,  calorimeter,  187 
Beggs,  James  &  Co.,  blower,  317 
Bell,  J.  Snowden,  quoted,  284 
Berthier's  calorimeter,  195 

results  PbO  tests,  194 
Biglow  Co. 's  boiler  setting,  219 
Bitumen,  no  organic  structure  in, 

18 
Bituminous  coal,  18 

ashes  from,  no 

calorific  value,  198 

classification  of,  22 

composition  of,  19 

table  of  American,  20 
Block  coal,  28 

ashes  from,  no 
Blossburg,  Pa.,  semi-bituminous 

coal,  1 8 

Blower,  steam,  argand,  317 
Boiler,  Barnes'  locomotive,  266 

efficiency,  216 

furnaces,  stationary,  217 
Kent's,  221 

horse-power,  180 

Strong's  locomotive,  280 

tubes  and  oil  fires,  302 

Wootten's  locomotive,  263 
Boyle's  law  and  density  of  air, 
76 


INDEX. 


339 


Breckenridge,  Ky. ,  cannel  coal, 

26 
Brick  arches  and  light  firing,  262 

and  soft  coal,  127 

construction  of,  251 

for  oil  burning,  300 

leaky  flues,  252 

locomotive,  250 

Murphy's,  124 

Southern    Pacific    Railway, 

288 

Bridge  wall,  locomotive,  265 
Briquettes  of  fuel,  42 
British  thermal  unit,  151 
Brown  coal,  29 

Thorp's  analysis,  30 
Buck  Mountain,  Pa.,  coal,  15 
Burlington,   C,    R.  •&  N   smoke- 
less firing,  123 

Burning    residuum   from    shale, 
298 

CAKING  coals,  22 

Calorie,   151 

Calorific  value  of  fuel,  178,  182 

Calorimeter,  Barrus',  187 

Berthier's,  195 

Carpenter's,  191 

copper-ball,  193 

Favre  &  Silberman's,  144 

Thompson's,  185 
Cannel  coal,  25 
Carbon,  160 

air  required  for,  81 

allotropic  states  of,  162 

and  hydrogen,  161 

dioxide,    see  Carbonic  Acid 

estimating    temperature    of 
combustion,  142 

heating  power  and  density, 
167 


Carbon  monoxide,  see  Carbonic 
Oxide 

specific  heat  of,  162 
Carbonic  acid,  161 

heat  units,  141 

in  the  air,  73 

Carbonic   acid  gas,  liquefaction 
of,  104 

measurement  of,  134 

properties  of,  104 
Carbonic  oxide,  161 

combustion  of,  105 

heat  units,  141 

liquefaction  of,  105 

properties  of,  105 
Carburetted  hydrogen,  170 
Carpenter,    R.    C.,    calorimeter, 

191 
Castle   Gate,    Utah,    bituminous 

coal,  284 
Charcoal,  composition,  165 

physical  properties,  164 
Chemical  action  and  mechanical 
energy,  149 

affinity,  62 

attraction,  63 

and  temperature,  66 

properties  of  a  body.  62 

separation,  energy  of,  66 
Chevandier,  M.,  quoted,  35 
Chimney,  309 

area  of,  311 

draft,  313 

height,  312 

increasing  draft  in,  316 

intensity  of  draft,  313 

object  of,  309 

proportions,   315 

table  of  dimensions,  316 

temperature,  economical,  31 4 

unbalanced  pressure  in,  309 


340 


INDEX. 


Centennial,  boiler  horse-power, 

181 

Centigrade  and  Fahrenheit  ta- 
ble, 56 

scale  of  temperature,  55 
Cincinnati  N.  O.  &  T.  P.   Rail- 
way smokeless  firing,  124 
Cinders,  collecting  in  front  end, 

279 

Clark,  D.  K.,  quoted,  199 
Cleaning  fires,  241 
Clinker,  114 

and    ashes,  locomotive    fire 

box,  291 

and  color  of  ashes,  1 1 1 
and  efficiency  of  coal,  117 
Coal,  10 

absorbs  oxygen,  331 
analysis     and     spontaneous 

combustion,  333 
and  oil,  relative  cost,  302 
ash-forming  constituents,  12 
commercial  classification,  n 
evaporation   by,   in   locomo- 
tives, 258 

evaporative  power  of,  181 
exposed  to  hot  surface,  335 
Gruner's  classification,  n 
height  of  pile,  fire  risk  in, 

335 

moisture  in,  172 
net  calorific  value,  182 
proximate  analysis  of,  172 
saved  by  light  firing,  260 
theoretical    calorific    value, 

182 

volume  of  gases  from,  310 
wet  and    spontaneous    com- 
bustion, 336 

where   it  goes  in  a  locomo- 
tive, 147 


Coke,  23 

calorific  value  of,  199 

coal    for    making  the   best, 
25 

from  lignite,  34 

properties  of,  24 
Colorado  lignite,  32 
Combining  weight,  58,  64 
Combustible,  equivalent  evapo- 
ration, 210 
Combustion,  83 

available  heat  of,  213 

chamber,  locomotive,  265 

effect  of  nitrogen,  72 

heat  developed  by,  144 

localization  of,  323 

nature  of,  83 

products- of,  103 

rate  of,  in  locomotives,  250 

spontaneous,  330 
Composition  of  fuel,  table,  10 
Compounds,    atomic    value    un- 
changed, 65 
Compressed   air,   operating  ash 

pan  by,  289 
Condensation   and    latent  heat 

204 

Conduction  of  heat,  153 
Conductivity  of  metals,  154 
Connellsville,  Pa.,  coke,  23 
Convection  of  heat,  155,  203 
Copper-ball  calorimeter,  193 
Corbus,  M.  D.,  and  brick  arches, 

252 

Coming's  patent  fuel,  460 
Corrugated  fire  box,  281 
Cost  of  oil  and  coal  compared, 

302 

Cotton  hulls?  feeding  to  furnace, 
247 

stalks,  evaporation  by,  198 


INDEX. 


341 


Cox,    E.  T.,  analysis  of  cannel 

coal,  27 

calorific  value  of  coal,  182 
Coxe  Bros.  &  Co.  standards  for 

small  coal,  14 
Culm,  16 

preparation  for  burning,  319 
Cumberland,  Md. ,  semi-bitumi- 
nous coal,  17 

DAILY  report,  travelling  fireman, 

291 
Damper,  317 

ash  pit,  322 

Definite  proportions,  law  of,  64 
Density  of  steam,  208 
Diamond,    physical    properties, 

163 
Diaphragm  in  smoke  box,  274 

plates,  279 
Dimensions,  boiler  furnace,  217 

chimneys,  316 
Dissipation  of  energy,  53 
Double     furnaces,     locomotive, 
Barnes',  267 

locomotive,  Strong's,  281 
Down-draft  furnace,  224 
Draft,   advantages  of  mechani- 
cal, 328 

appliances,  efficiency  of,  276 

best  variety  of  fan  for,  328 

caused     by     expansion     of 
gases,  155 

chimney,  estimating,  312 
how  modified,  316 

distribution  of,  279 

forced,  320 

furnace,  how  caused,  309 

induced  system  of,  325 

locomotive,  270,  283 

mechanical,  320 


Draft  pipes,  274 

double,  278 

sluggish  in  chimneys,  316 
Dry  coals,  defined,  12 
Dulong's  formula,  183 

ECONOMETER,  Arndt's,  132 

and  air  supply,  136 

detects  fuel  loss,  138 
Efficiency,  furnace,  215 

how  measured,  216 

locomotive  boiler,  259 
Elementary  analysis,  160 
Energy,  50 

characteristics  of,  51 

chemical  separation,  66 

dissipation  of,  53 

fuel,  52 

kinetic,  51 

potential,  50 
Equivalent,  63 

evaporation,  factors  of,  207 

from  and  at  212°,  210 
Escaping  gases  and  temperature 

of  steam,  203 

Evaporation    and    horse-power, 
180 

factor  of,  205 

latent  heat  of,  203 

locomotive,  258 

moisture  in  coal,  179 

object  of  reducing  to,  from 
and  at  212°,  213 

ordinary  rate  of,  213 

per  pound  combustible,  210 
Evaporative  factor,  defined,  12 

power  of  coal,  181 

results  in  locomotives,  271 
Exhaust  nozzle  for  oil,  302 

pipe  and  nozzle,  S.  P.  Ry. , 
285 


342 


INDEX. 


Exhaust  pipe  passages,  277 

single,  277 

single  and  double,  271 
steam,  heat  lost  in,  205 
utilizing  heat  in,  280 
tip,  adjustable,  278 

best  form,  271 

cross  bar  in,  278 

size  of,  272 

Expansion  of  air  by  heat,  151 
of  gases,  table  of,  150 

FACTOR  of  evaporation,  205 
Fahrenheit     scale    of    tempera- 
ture, 55 

Fan  for  forced  draft,  326 
Fat  coals,  defined,  u 
Favre  and  Silberman's  calorim- 
eter, 145 
Feed  water,  limit  of  temperature 

in  locomotives,  280 
Findlay,  O.,  natural  gas,  174 
Fire,  cleaning  of,  241 

temperature  of,  142 
Fire  box,  corrugated,  Strong's, 

280 

disadvantages  of  wide,  266 
for  straw  and  coal,  243 
limitations,  locomotive,  249 
objections  to  long,  249 
wide,  locomotive,  263 
with  two  furnaces,  266 
Fire    door,  instructions   regard- 
ing, 126 
Firing,  best  method,  261 

intelligent,     and    promotion 

for,  126 
light  and  boiler  repairs,  262 

and  brick  arches,  262 
practical  suggestions,  261 
saving  by  light,  260 


Firing,  single  shovel,  259 

Southern     Pacific    Railway, 

284 

Fisher's  bagasse  furnace,  241 
Flame,  90 

anthracite  coal,  101 
blue  region  in,  94 
candle,  hollow,  95 
carbonic  oxide,  105 
cause  of  luminosity  in,  97 
chemical  processes  in,  90 
color  in,  98 
dark  region  in,  93 
extinguished  by  cooling,  100 
faintly  luminous  region,  94 
not  a  continuous  process,  96 
not  in  contact  with  orifice, 

100 

proof  of  solid  carbon  in,  97 
rate  of  propagation,  95 
structure  of,  91 
successive  developments  in, 

92 
.     temperature  of,  99 

variations  of  temperature  in, 

96 

yellow  region  in,  93 
Flues,    leaky,    and    brick    arch, 

252 

cause  of,  253 
Forced  draft,  320 

best  fan  for,  326 
ventilation  of  coal  piles,  336 
French  unit  of  heat,  151 
Frontenac,  Kan.,  coal,  190 
Front    ends,    Southern     Pacific 

Railway  locomotive,  285 
Fuel,  9 

analysis,  160 

and  horse-power  unit,  181 

calorific  power  of,  180 


INDFX. 


343 


Fuel,  elementary  constitution,  9 
energy  of,  52 

feeding  fine,  to  furnace,  245 
fine,  preparation  of,  319 
Rogers  feeder,  247 
liquid,  advantages  of,  295 
loss  with  2  to  15  per  cent. 

CO2  in  gases,  137 
preparation  of,  for  steam  jet, 

3i9 

Furnace,   boiler,   dimensions  of, 
217 

bagasse,  241 

coals,  defined,  12 

door,  Southern  Pacific  Rail- 
way, 287 

double,  locomotive,  281 

down-draft,  224 

efficiency  of,  215 

feeder  for  fine  fuel,  245 

Kent's,  boiler,  221 

locomotive,  double,  266 

losses  in,  215 

Murphy's,  233 

stationary,  details  of,  215 
Fusion,  latent  heat  of,  156 

GAS  coals,  12 

Gas,  compared  with  coal,  174 

effects  of  heat  upon,  150 

evaporative  power  of,  175 

natural,  174 

producer,  176 

rate  of  expansion,  55 

Siemen's,  177 

water,  176 
Gaseous  fuels,   calorific  values, 

177 

Gases,   conduction   of    heat    in, 
155 

ignition  temperature  of,  87 


Gases,    rate  of   increase  in  vol- 
ume, 310 

volume  of  escaping,  310 
weight  of,  from  furnace,  107 
Georges  Creek  coal,  190 
Gordon's  hollow  blast  grate,  324 
Grant's  patent  fuel,  45 
Graphite,     physical     properties, 

164 
Grate  area,  advantages  of  large, 

249 

increase    of,    in   locomo- 
tives, 264 
hollow-blast,  324 
McClave's,  239 
plain,  locomotive,  255 
shaking,  details  of,  257 

Southern     Pacific    Rail- 
way, 289 
water-tube,  254 
when  to  be  shaken,  126 
Grimshaw,  Robert,  quoted,  255 
Gruner's  classification  of  coals, 


HAS  WELL,    C.   H.,   table,  proper- 
ties of  steam,  208 
Heat,  140 

Heat  and  chemical  action,  149 
mechanical  energy,  158 
water,  202 
work,  53 

combustion  of  carbon,  143 
conduction  of,  153 
convection  of,  155,  203 
developed     by    combustion, 

140,  144 

distribution    of,   in    locomo- 
tives. 147 

effect  upon  gases,  1 50 
upon  water,  149 


344 


INDEX. 


Heat    evolved    by    calorimeter 

tests,  146 

by  combustion,   194 
good  conductors  of,  154 
imperfect  conductors  of,  154 
how  gases  conduct,  155 
in  exhaust  steam,  utilizing, 

280 

in  steam,  208 
latent,  156 

lost,  burning  to  carbonic  ox- 
ide, 141 
mechanical     equivalent    of, 

157 

non-conductors  of,  154 
problem  in  steam  engine,  201 
radiation  of,  156 
specific,  159 
Heat,  unit  of,  151 

carbon  burned   to    CO    and 

C02,  141 
natural  gas,  174 
Heating  power  of  fuels,  178 
petroleum,  296 
sulphur,  148 

Heggem's     straw-burning     fur- 
nace, 243 

Height  of  chimney,  317 
Heintselman's  grate,  288 
Hoadley,  J.  C.,  quoted,  107 

temperature  tests,  203 
Horse-power  of  boilers,  180 

unit  of,  49 

Hot-steam  pipes  and  wood  igni- 
tion, 334 
Howard,  C.  C.,  analysis  natural 

gas,  175 

Hydrocarbon  oil  burner,  303 
from  shale,  298 
fuel  for  locomotives,  295 
Hydrogen,  168 


Hydrogen,  air  for  combustion  of , 

81 

liquefaction  of,  169 
product    of    combustion    of, 

103 

specific  heat  of,  152 
union  with  carbon,  84 
Hygroscopic  moisture,  172 

IGNITION,  86 

temperature  of  gases,  87 
Indiana  block  coal,  28 
Induced  system  of  draft,  325 
Injectors,  limit  of  feed  tempera- 
ture, 280 

Instructions  to  locomotive  fire- 
men, 125 
Internal  work  in  liberating  gas 

from  bituminous  coal,  182 
Iron  pyrites  and  ashes,  112 

and    spontaneous    com- 
bustion, 332 

JONES'  underfeed  stoker,  237 
Joule's  equivalent,  157 

KENT,  WILLIAM,  quoted,  184 
Kent's  boiler  furnace,  221 
Kentucky  brown  coal,  30 
Kinetic  energy,  51 

LATENT  heat,  156 

and  condensation,  204 
of  evaporation,  263 
of  fusion,  156 
Lean  coals  defined,  n 
Lehigh  anthracite  coal,  14 
Lesley,  J.  P.,  on  anthracite  for- 
mation, 13 

Light    firing,    Southern    Pacific 
Railway,  291 


INDEX. 


345 


Lignite,  30 

ashes  from,  34 

calorific  value  of,  198 

coke  from,  34 

composition  of,  32 

occurrence,  31 

properties  of,  30 

Lime,  how  present  in  ashes,  117 
Liquefaction,  interior  work,  156 
Liquids  bad  conductors  of  heat, 

154 
Locomotive,  air  and  steam  jets 

for,  129 

boiler,  Barnes',  266 
efficiency,  259 
Strong's,  280 
Wootten's,  262 
brick  arch,  250 
changing  coal  to  oil,  299 
combustion  chamber,  265,  280 
draft  in,  270 

evaporative  performance,  2 59 
fire  boxes,  smokeless,  123 
double,  266,  280 
limitations,  249 
wide,  263 

firing  instructions,  125 
furnace  details,  249 
rate  of  combustion,  250 
Smoke  Preventer  Co.,  127 
smokeless  combustion,  284 
where  the  coal  goes,  147 
Losses  in  a  furnace,  215 
Lost  work,  48 

MAHLER'S  formula,  184 
Mariotte's   law   and    density  of 

air,  76 

Marsh  gas,  170 
Master  Mechanics  Association — 

front  ends,  285 


McArdle,  Frederick,  quoted,  260 
McClave,  grate  by  James  Beggs 

&  Co.,  239 

McHenry,      E.      H. ,     diagram : 

"Where   the  coal    goes   when 

burned    in   a    locomotive    fire 

box, "  148 

Mechanical  draft,  advantages  of, 

320,  328 

energy  and  heat,  158 
equivalent  of  heat,  157 
stoker,  American,  235 

Ayers  and  Ranger,  231 
Babcock  &  Wilcox,  226 
Jones,  237 
Roney,  227 
Wilkinson,  229 
Mercury,  boiling  point  of,  54 

freezing  point  of,  54 
Metals,  thermal  conductivity  of, 

154 

Mogul  engine,  148 
Moisture  in  coal,  172,  180 
Molecule,  59 
Multiple    proportions,    law    of, 

65 
Murphy,  J.    W.,   locomotive  fire 

box,  124 
Murphy's  furnace,  233 

NAGLE,  A.  F.,  quoted,  29 

Natural  gas,  174 

heat  units  in,  174 
Howard's  analysis,  175 

Netting,  area  of  openings,  279 
location  of,  278 

New  River  coal,  190 

Nicholson,   George    B. ,    quoted, 

253 
Nitrogen,  71 

economic  qualities  of,  73 


INDEX. 


Nitrogen  in  products  of  combus- 
tion, 106 

liquid  and  solid,  71 
negative  qualities  of,  72 
non-supporter     of     combus- 
tion, 71 

specific  heat  of,  71,  152 
Non-caking  coals,  burning  of,  28 
Non-condensing  engine,  heat  lost 

in,  205 
Northern  Pacific  Railway  Mogul 

engine,  148 
Notation,  symbolic,  60 

O'BRIEN  &  PICKLE'S  furnace,  224 

Oil,  advantages  of  as  fuel,  295 
and  coal,  relative  cost,  302 
auxiliary  to  coal,  298 
burner,  Prescott's,  303 
burning  locomotive,  change 

from  coal,  299 
locomotive,   size   of    ex- 
haust nozzle,  302 

Oil  fires  and  boiler  tubes,  302 
are  they  smokeless?  302 
no  air  admitted  above,  300 
no  limit  to  steaming  capac- 
ity, 303 
products  of  combustion,  302 

Oil  of  the  Pacific  coast,  301 

Olefiant  gas,  171 

Oxygen,  69 

absorbed  by  coal,  331 
and  litharge  fuel  tests,  196 
and     spontaneous     combus- 
tion, 71 

chemical  activity  of,  71 
estimation  of  volume,  86 
liquid  and  solid,  70 
specific  heat  of,  69,  152 
supporter  of  combustion,  85 


Oxygen,  union  with  carbon,  84 

Oxide,  defined,  70 

of  iron  in  coal  ashes,  112 
of  lead  calorimeter  tests,  194 

Ozone  in  the  atmosphere,  74 

PARROT  coal,  26 
Patent  fuels,  43 

Coming's,  46 

Grant's,  45 

Strong's,  45 

Warleck's,  43 
Peat,  37 

calorific  value  of,  198 

charcoal,  40 

classification,  41 

composition,  38 

density,  39 

occurrence,  41 

preparation  for  fuel,  40 
Percy,    John,    definition  of  coal 
(numerous  quotations   from), 
10 
Petroleum,  analysis  of,  296 

heating  power  of,  296 
Pictet,  Raoul,  liquid  oxygen,  70 
Pocahontas  coal,  190 
Potash,  carbonate  of,  116 

in  ashes  of  wood,  116 
Potential  energy,  50 
Power,  unit  of,  49 
Prescott,  George  W.,  oil  burner, 

303 
Pressure  of  atmosphere,  75 

unit  of,  75 
Producer  gas,  176 
Products  of  combustion,  103 

of  oil  fires,  302 
Properties   of    saturated   steam, 

208 
Proportions  for  chimneys,  315 


INDEX. 


347 


Proximate  analysis  of  coal,  172 
Purdue  University,  calorimeter, 

193 
locomotive  test,  275 


,  C.   H.,   quoted,  270  et 


seq. 


RADIATION  of  heat,  156 
Raps,  Henry,  quoted,  262 
Rate  of  combustion,  locomotive, 

250 

Red  Lodge  coal,  148 
Rice  hulls,    feeding  to  furnace, 

247 
Richter's  theory  of  spontaneous 

combustion,  331 
Ringlemann's  smoke  scale,  121 
Rogers'  furnace  feeder,  247 
Roney's  mechanical  stoker,  227 

SAWDUST,  feeding  to  furnace,  247 
Scale  and    corrugated    furnace, 

282 

Schenectady  locomotive,  284 
Semi-anthracite  coal,  16 
Semi-bituminous  coal,  17 
Shaking  grate,  257 

Southern    Pacific    Railway, 

289 
Shale,     hydrocarbon     residuum 

from,  298 
Sieman's  gas,  177 
Silica  in  ashes,  115 
Sinclair,    Angus,    quoted,     123, 

259 

Small,    H.    T.,    superintendent 
Southern  Pacific  Railway,  284 
Smoke,  defined,   118 

from  locomotives,  123 
oil  fires,  302 


Smoke,  indication  of  waste,   119 

intensity  of,  120 

prevention,  119,  127 

Ringlemann's  scale,  121 
Smoke  box,  diaphragm  in,  274 

extension,  object  of,  275 
Smokeless  combustion,  127,  284 

firing,  123,  260 

Southern    Pacific    Railway    ash 
pan,  289 

brick  arch,  288 

details  of  grate,  289 

exhaust  pipe  and  nozzle,  285 

front  end  of  locomotives,  285 

furnace  door,  287 

oil  for  fuel,  295 

oil-burning  device,  299 

smokeless  combustion,  284 

travelling  fireman,  291 
Sparks,    baffle  plates,  and    net- 
tings, 279 
Specific  heat,  159 

air,  82,  143 

and  atomic  weight,  152 

ashes,  109 

carbon,  162 

gases,  152 

nitrogen,  71 

of  oxygen,  69 

solids,  table  of,  153 

water,  153 
Splint  coal,  12 
Spontaneous  combustion,  330 

and  coal  analysis,  333 
iron  pyrites,  332 

Richter's  theory,  331 

sulphur,  331 
Stack  and  baffle  plates,  279 

diamond     and    draft    pipe 
279 

locomotive,  best  form,  273 


348 


INDEX. 


Stack,    taper    better    than    dia- 
mond, 278 

Standards  of  temperature,  54 
Stationary  furnace  details,  215 
Stations,  preparing  tire  for,  126 
Steam  and  air  jets  in  locomotive 

furnaces,  objections  to,  131 
Steam  blower,  best  location,  318 
Steam,  condensation  of,  204 
effect  of,  in  furnace,  319 
engine,  heat  problem  in,  201 
generation  of,  201 
heat  lost  in  exhaust,  205 
neating,  209 
jets   for  smoke  prevention, 

127 

properties  of,  208 
total  heat  in,  207 
withdrawal  of  heat  from,  209 
Stokers,    mechanical,    Ayers    & 

Ranger,  231 
Babcock  &  Wilcox,  226 
Roney,  227 
Wilkinson,  229 
Straw-burning  furnace,  243 

evaporation  by,  198 
Strong,    G.    S.,    locomotive    fire 

box,  280 

Strong's  patent  fuel,  45 
Sturtevant,    B.    F.    Co.,    ash-pit 

dampers,  322,  324 
forced-draft  system,  320 
induced-draft  system,  325 
Sulphur,  168 

and     spontaneous    combus- 
tion, 331 

combustion  of,  106 
heating  power  of,  148 
in  coal,  173 

effects  of,  106 
occurrence,  113 


Sulphurous  oxide,  106 
Symbolic  notation,  60 

and  atomic  weight,  61 

TAMAQUA,    Pa.,  anthracite    ioal, 

14 

Tan  as  a  fuel,  37 

Temperature   best  for   chimney 

draft,  313 

burning  carbon,  142 
chimney,  economical,  314 
fire,  conditioned,  142 
gases  and  steam,  203 
range  in  steam  engine.  202 
standards  for,  54 
steam,  208 

Texas  lignite,  34 

Thermal  unit,  British,  151 
French,    151 

Thermometer,  53 

and  quantity  of  heat,  57 
indicates  sensible  heat,  57 

Thompson's  calorimeter,  185 

Thorpe,      Professor     (numerous 
quotations  follow),  42 

Total  heat  in  steam,  267 

Travelling     fireman,     Southern 
•     Pacific  Railway,  291 

Tunnels,     preparing     fire     for, 
125 

UNIT     of     boiler     horse-power, 
i  So 

British  thermal,  151 

French  thermal  151 

horse-power,  49 

power,  49 

pressure,  75 

work,  48 
Useful  work,  49 
Utah  bituminous  coal,  284 


INDEX. 


349 


VACUUM  in  locomotive  fire  boxes, 

277 

Vancouver's  island  lignite,  33 
Vapor  of  water  in  atmosphere, 

74 

Velna's  fuel  briquettes,  42 
Violette,  M..  quoted,  36 
Volume  of  one  pound  steam,  208 

WASHINGTON  lignite,  32 
Water,  boiling  point,  55 

conducts  heat  slowly  down- 
ward, 202 

effect  of  heat  upon,  149 
freezing  point  of,  55 
specific  heat  of,  153 
Webber,  W.  O.,  quoted,  259 
Webster,  Hosea,  on  natural  gas, 

175 
Weight  of  the  air,  75 

of  steam,  208 

Wilkesbarre,    Pa. ,    semi-anthra- 
cite, 15 


Wilkinson's  mechanical  stoker 

229 
Wood  as  a  fuel,  36 

calorific  value  of,  197 

classification  of,  34 

composition  of,  35 

in  coal  liable  to  self-ignition, 

334 

moisture  in,  35 
spontaneous      ignition      of, 

334 

Wootten,  John  E.,  boiler,  263 
Work,  48 

and  heat,  53 

lost,  48 

unit  of,  48 

useful,  49 

YOUGHIOGHENY  coal,  190 

ZERO,  absolute,  54 
Centigrade,  55 
Fahrenheit,  55 


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JUST  PUBLISHED. 


Prevention  of  Railroad  Accidents 

OR 

Safety  in  Railroading 

By  GEORGE  BRADSHAW 

POCKET  SIZE  p   .  ,-fl  FULLY 

192  PAGES  race,  ouc.  ILLUSTRATED 

A  HEART-TO-HEART  talk  with  Railroad  Employes, 
dealing  with  facts,  not  theories,  and  showing  the 
men  in  the  ranks,  from  every -day  experience,  how 
accidents  occur  and  how  they  may  be  avoided.  The 
book  is  illustrated  with  seventy  original  photographs 
and  drawings  showing  the  safe  and  unsafe  methods  of 
work.  No  visionary  schemes,  no  ideal  pictures.  Just 
plain  facts  and  Practical  Suggestions  are  given.  Every 
railroad  employe  who  reads  the  books  is  a  better  and 
safer  man  to  have  in  railroad  service.  It  gives  just 
the  information  which  will  be  the  means  of  preventing 
many  injuries  and  deaths. 

The  author  of  this  work  is  employed  by  the  N.  Y.  C.  &  H.  R.  R.R. 
in  special  service  for  the  prevention  of  accidents.  For  many  years  he 
has  been  constantly  engaged  in  the  study  of  railroad  accidents,  and 
from  the  mass  of  facts,  obtained  by  years  of  study,  he  has  formed 
certain  conclusions  as  to  the  prevention  of  accidents. 

One  of  these  conclusions  is  that  the  majority  of  preventable  acci- 
dents are  due,  not  to  defective  material  or  improper  method,  but  to 
the  men  themselves.  While  considerations  of  safety  still  call  for 
much  improvement  in  physical  conditions,  it  is  a  fact  that  in  no  field 
of  activity  has  there  been  greater  material  advancement  than  in  rail- 
roading. Yet  the  record  of  injury  to  employes  has  been  growing 
worse  every  year. 

This  work  takes  up  the  human  element  in  a  heart-to-heart  talk 
with  employes.  It  show  them  (1)  the  seriousness  of  the  personal  in- 
jury problem  and  that  they  are  the  real  sufferers  from  present  condi- 
tions ;  and  (2)  how  they  themselves  are  responsible  for  the  personal 
injury  record  and  how  they  can  improve  it. 


All  Railroad  Employes  should  procure  a  copy,  read  it, 
and  do  their  part  in  preventing  accidents. 


A  NEW  REVISED  EDITION.    JUST  PUBLISHED. 

UP-TO-DATE 

AIR-BRAKE  CATECHISM 

By  ROBERT  H.  BLACKALL 


Pocket  Size  Price    $2  00         Fully  Illustrated 

384  Pages.  rilCC,  *^.UU         With  ColaMA  plateat 


IS  is  the  standard  book  on  the  Air  Brake,  written  by  one  of  the 
.      most  widely  known  Air  Brake  Men  in  the  United  States,  Canada 

and  Mexico.  It  is  a  practical  and  complete  study  of  the  air 
brake,  including  the  E-T  Locomotive  Brake  Equipment,  the  K  (Quick 
Service)  Triple  Valve  for  Freight  Service,  the  Type  L  High-Speed 
Triple  Valve,  and  the  Cross  Compound  Compressor.  The  operation  of 
all  parts  of  the  apparatus  is  explained  in  detail  and  a  practical  way 
of  locating  their  peculiarities  and  remedying  their  defects  is  given. 

If  you  are  preparing  for  an  examination,  you  should  secure  a  copy 
of  this  book  at  once,  as  it  contains  over 

2,000  QUESTIONS  WITH  THEIR  ANSWERS 

This  is  the  only  book  which  has  been  endorsed  and  used  by  Air 
Brake  Instructors  and  Examiners  on  the  different  roads  throughout 
the  United  States. 

CONTAINING  CHAPTERS  ON 

I.-BEGINNINGS  OF  THE  AIR  BRAKE. 
II  __  THE  WESTINGHOUSE  TRIPLE  VALVES. 
III.—  WESTINGHOUSE  FREIGHT  EQUIPMENT. 
IV.—  WESTINGHOUSE  AIR  PUMPS. 
V.—  MAIN  RESERVOIR. 

VI.—  WESTINGHOUSE  OLD-STYLE  HIGH-SPEED  BRAKE 
VII.—  NO.  6  E-T  LOCOMOTIVE  BRAKE  EQUIPMENT. 
VIII.—  AIR  SIGNAL  SYSTEM. 
IX.-BRAKING  POWER  AND  LEVERAGE. 
X.—  THE  SWEENEY  COMPRESSOR. 
XI.—  TRAIN  INSPECTION. 

XII.-FORMULAE  AND  RULES   FOR  AIR    BRAKE    IN- 
SPECTORS. 


REMEMBER    THAT    THIS     BOOK    GIVES    FULL    AND 

LATEST  INFORMATION  ON  THE  OLD  AS  WELL 

AS  THE  LATEST  AIR  BRAKE  EQUIPMENT 


REVISED  POCKET  EDITION 

LOCOMOTIVE  BREAKDOWNS 
AND  THEIR  REMEDIES 

By  GEO.  L.  FOWLER,  revised  by  WM  W.  WOOD,  Air  Brake  Instructor 
270  Pages  PRICE  $1.00      Fully  Illustrated 

ENGINEERS  are  paid  nowadays  for  getting  their 
engines  into  the  terminal  on  time,  and  to  accom- 
plish this  there  must  be  no  casualties  EN  ROUTE  that 
will  cause  delay ;  accidents,  however,  will  happen,  and 
it  is  the  knowledge  of  HOW  TO  AVOID  DELAY  IN 
CASE  OF  ACCIDENTS  that  the  Company  requires  of 
engineers  nowadays,  and  what  to  do  in  case  of  break- 
downs. The  revised  pocket  edition  of  "Locomotive 
Brakedowns ' '  is  absolutely  necessary  to  every  engineer, 
fireman,  and  shop  man,  because  it  treats  of  every 
possible  engine  trouble,  and  presents  the  remedy,  in 
the  form  of  questions  and  answers.  Just  imagine  all 
the  common  troubles  that  an  engineer  may  expect  to 
happen  sometime,  and  then  add  all  of  the  unexpected 
ones,  troubles  that  could  occur,  but  that  you  had  never 
thought  about,  and  you  will  find  that  they  are  all  here, 
in  this  Up-to-Date  Edition  of  "Breakdowns,"  with.the 
very  best  methods  of  repair. 

CONTENTS 


I.— Defective  Valves;  IL— Accidents  to  the  Valve  Motion; 
HI. — Accidents  to  Cylinders,  Steam  Chests,  Cylinders  and  Pistons; 
IV.— Accidents  to  Guides,  Crossheads  and  Rods  ;  V,  -The  Walschaert 
Valve  Motion  ;  The  Baker- Pillord  Improved  Valve  Gear  ;  Accidents 
that  May  Happen  to  these  Gears ;  VI.— Accidents  to  Running  Gears ; 
VII. -Truck  and  Frame  Accidents ;  VIII.-  Boiler  Troubles ;  IX.— 
Defective  Throttle  and  Steam  Connections;  X.— Defective  Draft 
AppMances ;  XI.— Pump  and  Injector  Troubles  ;  XII.— Accidents  to 
Cab  Fixtures;  XIII.— Tender  Accidents;  XIV. -Miscellaneous 
Accidents:  XV.— Compound  Locomotive  Accidents;  XVI.— Tools 
a»*d  Appliances  for  Making  Engine  Repairs ;  XVII.— Air  Brake 
Troubles ;- XVIII.— The  Pyle-National  Electric  Headlight. 


JUST   PUBLISHED! 

PRACTICAL  INSTRUCTOR 
AND  REFERENCE  BOOK  FOR 

LOCOMOTIVE  FIREMEN  AND  ENGINEERS 

By  CHARLES  F.  LOCKHART 

368  Pages.  PRICE,  $1.50       88  Illustrations. 

THIS  book  treats  in  a  thorough  manner  of  the 
rail  road  man's  duties  and  how  to  properly  per- 
form them.  It  also  contains  practical  information  on : 
The  Construction  and  Operation  of  Locomotives; 
Breakdowns  and  Their  Remedies;  Air  Brakes  and  Valve 
Gears.  Rules  and  Signals  are  handled  in  a  thorough 
manner.  As  a  book  of  reference  it  cannot  be  excelled. 
An  entirely  new  book  on  the  Locomotive.  It 
appeals  to  every  rail  road  man,  as  it  tells  him  how 
things  are  done  and  the  right  way  to  do  them.  Written 
by  a  man  who  has  had  years  of  practical  experience 
in  locomotive  shops  and  on  the  road  firing  and  running. 
The  information  given  in  this  book  cannot  be  found  in 
any  other  similar  treatise.  Eight  hundred  and  fifty-one 
questions  with  their  answers  are  included  which  will 
prove  specially  helpful  to  those  preparing  for  ex- 
amination. 

THE  BOOK  IS  DIVIDED  INTO  SIX  PARTS,  AS  FOLLOWS: 

Part  I.— THE  FIREMAN'S  DUTIES. 

Part  II.— GENERAL  DESCRIPTION  of  the  LOCOMOTIVE. 

Part  III.-BREAKDO WNS  AND  THEIR  REMEDIES* 

Part  IV.- AIR  BRAKES. 

Part  V.— EXTRACTS  FROM  STANDARD 

P»r*.  VT.— QUESTIONS  FOR  EXAMINATION. 


JUST    PUBLISHED  NEW  POCKET  EDITION 

WESTINGHOUSE  E-T  AIR  BRAKE 
INSTRUCTION  POCKET  BOOK 

By  WM.  W.  WOOD,  Air  Brake  Instructor 

PRICE  $1.50 

CONTAINS  examination  questions  and  answers  on 
the  E-T  equipment.  Covering  what  the  E-T, 
Brake  IS.  How  it  should  be  OPERATED.  What  to 
do  when  DEFECTIVE.  Not  a  question  can  be  asked 
of  the  ENGINEMAN  UP  FOR  PROMOTION  on  either 
the  No.  5  or  the  No.  6  E-T  equipment  that  is  not 
asked  and  ANSWERED  in  the  book.  If  you  want  to 
thoroughly  understand  the  E-T  equipment  get  a  copy 
of  this  book.  It  covers  every  detail.  Makes  Air  Brake 
troubles  and  examinations  easy. 

AMONG  THE  CONTENTS  OF  THIS  BOOK  ARE; 

The  No.  6  E-T  Equipment— the  Valve— the  Piping— the  Gauges. 
The  theory  of  the  Triple  Valve,  and  its  principle  in  application  to  the 
E-T  Locomotive  Brake.  The  Distributing  Valve-Colored  Chart* 
showing  each  and  every  phase  of  its  action  accompanied  by  Colored 
Piping  Diagrams  indicating  the  contained  pressures.  Theory  of  the 
Quick- Action  Triple  Valves,  its  Importance— its  Principle  in  Appli- 
cation to  the  Quick-Action  Distributing  Valve  of  the  No.  6  type.  The 
E-6  Safety  Valve.  The  H-6  Automatic  Brake  Valve— theory  and 


Hscharge  Valve- Construction  of  the  H-6  Brake  Valve.  Trans- 
parency Plates  in  Color  Tints  showing  the  Rotary  Valve,  and  through 
it  the  Rotary  Valve  Seat,  Ports,  etc.,  in  each  Operative  position  of  the 
Brake  Valve  Handle.  The  S-6  Independent  Brake  Valve— Its  Con- 
struction. Transparency  Plates  similar  to_  those  of  the  H-6  Brake 
Valve,  showing  the  arrangement  of  Ports  in  Rotary  Valve  and  Seat 
in  each  position.  The  Double-Pressure,  B-6  Feed  Valve.  The 
Duplex  automatically  controlled  Excess  and  Maximum  Pressure 
Pump  Governor.  The  C-6  Reducing  Valve.  The  "Dead  Engine 
Feature"  of  the  No.  6  E-T  Equipment.  Combined  Air  Strainer  and 
Check  Valve— its  application  to  the  Train  Air  Signal  System. 

Operation  of  the  No.  6  E-T  Locomotive  Brake— Freight  Service- 
Passenger  Service— Switching  Service— General  Braking  Service — 
Grade  Work,  etc.  Reporting  Work  on  the  No.  6  Equipment.  Testing; 
the  Equipment.  Leaking  or  Broken  Pipes  of  No.  6  Equipment. 

The  No.  6  E-T  Locomotive  Brake  Equipment— Its  distinctive 
features  as  compared  with  the  No.  6  Type— Its  Operation— Leaking; 
or  Broken  Pipes  in  the  No.  5  Equipment. 

Filled  with  Colored  Plates -Showing  Yarious  Pressure* 


JUST  OFF  THE  PRESS.  POCKET  EDITION. 


TRAIN  RULE  EXAMINATIONS 
MADE  EASY 

By  G.  E.   COLL1NGWOOD 

256  Pages —Fully  Illustrated  DDI/T     fct   Off 

with  Train  Signals  in  colors  n\lV*H    $  1  .<£«> 

THIS  is  a  book  which  every  railroad  man,  no  matter 
what  department  he  is  in,  should  have,  as  it  is 
written  by  a  man  who  understands  the  subject  thor- 
oughly. Mr.  G.  E.  Collingwood,  the  author,  is  a 
recognized  authority  on  train  rules  and  train  orders. 
For  years  he  has  edited  the  train  rule  department  in 
four  of  the  foremost  railroad  magazines  in  the  United 
States.  If  you  want  to  thoroughly  understand  the 
subject  get  a  copy  of  this  book,  as  every  detail  is 
covered,  and  puzzling  points  are  explained  in  simple, 
comprehensive  language.  This  book  is  the  only 
practical  work  on  train  rules  in  print. 

Contains  complete  and  reliable  information  of  the 
Standard  Code  of  Train  Rules  for  single  track.  Shows 
Signals  in  Colors,  as  used  on  the  different  roads. 
Explains  fully  the  practical  application  of  train  orders, 
giving  a  clear  and  definite  understanHiftg  of  all  orders 
which  may  be  used.  The  meaning  and  necessity  for 
certain  rules  is  explained  in  such  a  manner  that  the 
student  may  know  beyond  a  doubt  the  rights  conferred 
under  any  orders  he  may  receive  or  the  action  required 
by  certain  rules* 

Nearly  500  Questions  with  their  Answers  are  Included 
AMONG  THE  SUBJECTS  TREATED  ARE 

The  American  Railway  Association ;  Standard  Time ;  Dividing 
points  between  the  Time  Sections ;  Personal  Admonition ;  Defin- 
itions of  Terms  used;  Time-Tables;  Signals;  Use  of  Signals; 
Superiority  of  Trains ;  Movement  of  Trains ;  Train  Orders;  Forms 
of  Orders;  Combinations  of  Orders;  Clearance  Cards;  Train 
Identification;  Examination  Questions;  Answers  to  Examination 
Questions;  Standard  Code  of  Train  Rules  for  Siugle  Track; 
Diagrams  of  Hand,  Flag  and  Lamp  Signals  in  Colors,  etc. 


JUST   PUBLISHED 
THIRD    EDITION,    REVISED    AND    ENLARGED 

THE  WALSGHAERT  and  OTHER  MODERN 
RADIAL  VALVE  GEARS  FOR  LOCOMOTIVES 

By  WM.  W.  WOOD,  Air  Brake  Iiupector 
245  Pages  PRICE,  $1.50 


WITH  the  adoption  of  the  Walschaert  Valve  Gear 
on  nearly  every  modern  locomotive  in  America, 
this  book  fills  a  place  of  real  interest  and  usefulness. 
By  a  careful  study  of  its  pages,  one  can  THOROUGHLY 
understand  the  Walschaert  Valve  Gear,  as  the  author 
takes  the  plainest  form  of  a  steam  engine  —  a  stationary 
engine—  in  the  rough,  that  will  only  turn  its  crank  in 
one  direction  —  and  from  it  builds  up  —  with  the  reader's 
help,  a  modern  locomotive  equipped  Tvith  the  Wal- 
schaert Valve  Gear,  complete. 

THE  CONTENTS  OF  THE  BOOK  ARE  DIVIDED  INTO  FIVE  PARTS 

THE  FIRST  DIVISION  contains  an  analysis  of    the  Walschaert 

Valve  Gear. 
THE  SECOND  DIVISION  treats  on  the  Designing  and  Erecting  of 

the  Valve  Gear. 
THE  THIRD  DIVISION  has  to  do  with  the  actual  work  of  the  Wal- 

schaert Valve  Gear  on  the  Road. 
THE  FOURTH  DIVISION  is  composed  entirely  of  questions  and 

answers  on  the  Walschaert  Valve  Gear. 
THE  FIFTH  DIVISION  deals  with  the  Setting  of  Valves  with  the 

Walschaert  Gear,  the  Hobart-Allf  ree  Valve  and  Valve  Gear,  and 

the  Baker-Pilloid  Vaive  Gear  in  its  original  and  improved  form. 

The  book  is  fully  Illustrated,  and  a  novel  and  inter- 
esting feature  of  the  book  is  tie.  folding  diagrams  with 
cardboard  valve  models,  by  means  of  which  the  actual 
operation  of  the  valve  under  the  influence  of  the  Wal- 
schaert motion  can  be  studied. 


NEW  EDITION  JUST   PUBLISHED 

LOCOMOTIVE    CATECHISM 

By  ROBERT  GR1MSHAW,  M.  E. 
825  Pages  437  Illustrations  and  Three  Folding  Plate* 

PRICE  $2.50 

THIS  book  commends  itself  an  once  to  every  Engineer 
and  Fireman,  and  to  all  who  are  going  in  for 
examination,  or  promotion. 

In  plain  language,  with  full,  complete  answers, 
not  only  all  the  questions  asked  by  the  examining 
engineer  are  given,  but  those  which  the  young  and  less 
experienced  would  ask  the  veteran,  and  which  old 
hands  ask  as  "stickers." 

It  is  a  veritable  Encyclopaedia  of  the  Locomotive, 
is  entirely  free  from  mathematics,  and  thoroughly  up-to- 
date.  Study  it  and  you  will  know  your  engine  thoroughly. 

CONTAINS  OVER  4000  EXAMINATION  QUESTIONS 
WITH  THEIR  ANSWERS. 

AMONG  SOME  OF  THE  SUBJECTS  TREATED  ARE; 

Accidents  and  Emergencies;  Air-Brakes;  Alfree-Hubbell 
Gear;  Allen  Gear;  Automatic  Reducing  Valve;  Automatic  Slack 
Adjuster;  Auxiliary  Reservoir;  Blower;  Boilers;  Brake  Cylin- 
der; Cab;  Check  Valve;  Collisions;  Combustion;  Compound 
Locomotives;  Crosshead  and  Guides;  Cut-off  and  Expansion; 
Cylinder ;  Derailment ;  Eccentric  Motion ;  Eccentric  Rods ;  Elec- 
tric Headlight;  Engine  and  Tender  Brakes ;  Engineman's  Tender 
Valve;  Equalizing  Bars;  Examination  of  Firemen;  Firing; 
Firing  with  Oil ;  Four-Cylinder  Compounds ;  Gears;  Gooch  Gear; 
Headlight;  Indicator:  Injector;  Joy  Gear;  K  Tripple  Valve; 
Knocks  and  Pounds;  Lubrication;  Piston  Valves;  "Quick- 
Action"  Brake :  Relief  Valves:  Richmond-Mellin  Compound  ;  Slide 
Valve;  Slide- Valve  Feed  Valve;  Superheated  Steam;  Sweeney 
Compressor;  Tandem  Compounds;  Three-Cylinder  Compounds; 
Vacuum  Brake;  Valve  Gears;  Valve  Motion,  Models;  Valve 
Betting ;  Walschaert  Gear ;  Young  Valve  Gear. 


LOCOMOTIVE 
BOILER  CONSTRUCTION 

By  FRANK  A.  KLEINHANS 

421  Pages  DDI/^I?      fcQ  Affc  Five  Folding 

350  Illustrations  rlUVJLp    *,5.UU  plateg 

THIS  IS  ONE  OF  THE  BEST  BOOKS  OP  ITS  KIND 
EVER  PUBLISHED.  IT  TAKES  THE  READER 
FROM  THE  LAYING  OUT  OF  THE  SHEETS 
TO  THE  COMPLETED  BOILER. 

•"THE  building  of  boilers  is  a  work  that  none  have 
*  attemped  to  describe  in  detail,  owing-  to  the 
necessity  of  knowing  each  operation  thoroughly  in 
order  to  do  it  justice.  Here  is  where  this  book  differs 
from  all  others.  Each  step,  from  the  first  mark  on 
the  sheet  to  the  finished  boiler,  receives  careful  atten- 
tion in  a  thoroughly  practical  way.  Locomotive  boilers 
present  more  difficulties  in  laying  out  and  building  than 
any  other  type,  and  for  this  reason  the  author  uses 
them  as  examples.  Anyone  who  can  handle  them  can 
tackle  anything.  This  book  takes  the  locomotive  boiler 
up  in  the  order  in  which  its  various  parts  go  through 
the  shop.  Give  details  of  construction ;  practical  facts, 
such  as  life  of  riveting,  punches  and  dies ;  work  done 
per  day,  allowance  for  bending  and  flanging  sheets, 
and  other  data. 

CONTENTS. 


LAYING  OUT  WORK. 

FLANGING  AND  FORGING,  PUNCHING,  SHEARING  and 

PLATE  PLANNING. 
BENDING. 

MACHINING  PARTS. 
BOILER  DETAILS. 
ASSEMBLING     AND     CALKING,      FINISHING      PARTS, 

BOILER  SHOP  MACHINERY. 
GENERAL  TABLES. 
PLATES  SHOWING  TYPES  OF  MODERN  LOCOMOTIVE 

BOILERS. 


LINK  MOTIONS,  VALVES  AND 
VALVE  SETTING 

By  FRED  H.  COLVIN 
FULLY  ILLUSTRATED  PRICE,  50c. 

A  HANDY  book  for  the  engineer  or  machinist  that 
clears  up  the  mysteries  of  valve  setting.  Shows 
the  different  valve  gears  in  use.  how  they  work,  and 
why.  Piston  and  side  valves  of  different  types  are 
illustrated  and  explained.  A  book  that  every  rail  road 
man  in  the  motive  power  department  ought  to  have. 

CONTAINS  CHAPTERS  ON 

Locomotire  Link  Motion.— Direct  and  Indirect  Mo- 
tion ;  lap ;  lead ;  crossed  rods,  etc. 

Valve  Movements.— Twelve  charts  showing  com- 
plete movements  of  valves  under  various  conditions  of 
travel ;  lap  and  lead. 

Setting  Slide  Valve. — Finding  dead  centers ;  increas- 
ing or  decreasing  leads ;  changing  length  of  eccentric 
rods  or  blades ;  moving  eccentrics  on  axle. 

Analysis  by  Diagrams.— Illustrates  the  various  con- 
ditions that  occur  with  direct  or  indirect  motion ;  inside 
and  outside  admission  and  different  methods  of  connect- 
ing the  link.  New  facts  and  rules  in  connection  with 
link  motions  and  valve  setting. 

Modern  Practice. — Shows  what  is  being  done  in  the 
matter  of  eccentric  rod  length  s ;  angularity  of  eccentric 
rods;  leads;  proportions  of  travel;  eccentric  throw; 
lap;  ports;  piston  speed,  etc. 

Slip  of  Block.— Illustrates  how  and  why  "Slip"  ex- 
ists and  how  it  is  hardly  considered  in  modern  practice. 

Slide  Valves.— Shows  balanced  D  Valve,  Allen  Valve 
and  Wilson's  American  Valve. 

Piston  Valves. — Shows  eight  varieties  of  piston 
valves;  two  styles  of  valve  bushings  or  cages  and  device 
for  getting  water  out  of  cylinder.  Gives  experience  of 
several  roads  with  piston  valves. 

Setting  Piston  Valves. — Plain  directions  on  points 
differing  from  slide  valves. 

Other  Valve  Gear*.— Joy- Allen,  Walschaert,  Gooch, 
411full-Hubbell,  etc. 


A    CATECHISM    ON    THE 

COMBUSTION  OF  COAL 

AND  THE  PREVENTION  OF  SMOKE 

By  WILLIAM  M.  BARR.,  M.  E. 
Nearly  350  Pages    PRICE   $1.00    Fully  Illustrated 

A    PRACTICAL    TREATISE    FOR 
Engineers,  Firemen  and  all  others  interested  in  Fuel  Economy. 

TO  be  a  success  a  fireman  must  be  "  Light  on  Coal."     He  must 

keep  his  fire  in  good  condition,  and  prevent,  as  far  as  possible, 

*  the  smoke  nuisance.    To  do  this,  he  should  know  how  coal  burns, 

how  smoke  is  formed  and  the  proper  burning  of  fuel  to  obtain  the 

best   results.       He   can   learn    this,    and   more   too,   from   Barr's 

"COMBUSTION    OF    COAL    AND    THE    PREVENTION    OF 

SMOKE."    It  is  an  absolute  authority. 

Contains  nearly  500  questions  with  their  answers, 
giving  the  needed  information  to  enable  anyone  to  pass 
any  examination  on  combustion. 

AMONG  THE  SUBJECTS  TREATED  ARE 

Locomotive  Furnace  Details.  Limitations  of  Locomotive  Fire- 
Box.  Advantages  of  large  Grate  Area.  Rate  of  Combustion  in 
Locomotive  Boilers.  Function  of  Fire- Brick  Arch  in  Locomotive 
Fire-Boxes.  Usual  Construction  of  Brick  Arch  in  Locomotive  Fire- 
Boxes.  Does  the  Brick  Arch  in  Locomotive  Fire-Boxes  cause  leaky 
Flues?  Tubular  Water  Grates.  Stationary  Coal  Burning  Grate. 
Shaking  Grate.  Comparison  of  Evaporated  Power  of  Anthracite  and 
Bituminuous  Coal  in  Locomotive  Practice.  Practical  results  of  single 
shovel  Firing  on  the  B.  C.  R.  and  N.  Ry.  Saving  in  Coal  by  light 
Firing  in  Locomotives.  The  best  Method  of  Firing  a  Locomotive. 
Noticeable  improvements  in  Connection  with  light  Firing  and  Boiler 
Repairs.  Direct  saving  upon  the  Brick  Arches  in  Locomotive  Fire- 
Boxes  by  Light  Firing.  Advantages  attained  by  the  lateral  exten- 
sion of  Locomotive  Fire-Boxes.  Disadvantages  of  a  wide  Fire-Box 
in  Locomotives.  Division  of  wide  Fire-Box  in  Locomotives  into  two 
separate  Furnaces.  Evaporative  results  in  ordinary  Locomotive 
Practice.  Most  efficient  form  of  Exhaust  Tip.  Size  of  average 
Exhaust  Tips.  Conclusions  reached  regarding  means  for  increase 
in  Production  of  Steam  by  Increased  Draft.  Strong's  Locomotive 
Fire-Box.  How  the  Smokeless  Combustion  of  Bituminuous  Coal  is 
carried  out  in  Pratice  in  Locomotives.  Details  of  front  ends  of  Loco- 
motives So.  Pac.  Ry.  Furnace  Door  Details.  Details  of  Shaking 
Grate.  Details  of  Ash  Pan.  Facts  given  in  daily  report  of  Traveling 
Firemen  So.  Pac.  Ry. 

Hydrocarbon  Oil  as  a  Fuel  for  Locomotives.  Heating  Power  of 
Crude  Petroleum.  Success  attending  the  use  of  Liquid  Fuel  as 
Auxiliary  to  Coal  for  Locomotive  Engines.  Changes  necessary  to 
Convert  a  Coal  into  an  Oil-Burning  Locomotive.  Construction  of 
Atomizers  for  Burning  Oil  on  So.  Cal.  Railroad.  How  Oil  is  supplied 
to  Burner  under  Pressure.  Size  of  Exhaust  nozzle  when  burning 
Oil.  Are  Oil  Fires  Smokeless?  Effect  of  Products  of  Combustion  of 
an  Oil  Fire  upon  the  Tubes  of  a  Boiler.  Relative  cost  of  Oil  and 
Coal  as  a  Fuel  in  Locomotive  Practice. 


THE  APPLICATION  OF  HIGHLY 

SUPERHEATED  STEAM  TO  LOCOMOTIVES 

By  ROBERT  GARBE 

Edited  by  LESLIE  S.  ROBERTSON 

Very  fully  Illustrated  with  Folding  Plates  and  Tables 

PRICE,  $2.50 

A  PRACTICAL  work  specially  prepared  for  the  use 
•**•  of  all  interested  in  the  application  of  superheated 
steam  to  locomotives,  written  by  a  man  who  probably 
has  had  greater  experience  and  is  more  thoroughly 
familar,  in  a  practical  way,  with  superheated  steam  in 
locomotive  practice  than  any  other  man  on  either  conti- 
ent.  While  the  book  deals  with  highly  superheated 
steam,  the  matter  of  low  superheat  is  thoroughly  dis- 
cussed. In  addition  to  the  theoretical  discussion  of  the 
subject  the  book  also  contains  full  illustrated  descrip- 
tions, with  a  discussion  of  the  merits,  of  all  the  better 
known  superheaters  in  the  world.  The  details  of  the 
locomotive,  outside  of  the  superheater,  for  satisfactorily 
using  steam  at  this  high  temperature  are  discussed  and 
the  designs  introduced  by  Herr  Garbe  are  illustrated. 
Reports  on  a  number  of  very  complete  and  practical 
tests  form  the  concluding  chapter  of  the  work.  This 
book  cannot  be  recommended  too  highly  to  those  motive 
power  men  who  are  anxious  to  maintain  the  highest 
efficiency  in  their  locomotives. 

CONTAINS  CHAPTERS  ON 

I.— GENERATION  OF  HIGHLY  SUPEBHE ATED  STEAM. 

II.-SUPER HEATED  STEAM  AND  THE  TWO-CYLINDER 
SIMPLE  ENGINE. 

III.— COMPOUNDING  AND  SUPERHEATING. 

IV.— DESIGNS  OF  LOCOMOTIVE  SUPERHEATERS. 

V.— DESIGNS  OF  LOCOMOTIVE  SUPERHEATERS.-cont'd 

VI.— CONSTRUCTIVE  DETAILS  OF  LOCOMOTIVES  US- 
ING HIGHLY  SUPERHEATED  STEAM. 

VII.— EXPERIMENTAL  AND  WORKING  RESULTS  WITH 
SUPERHEATED  STEAM  LOCOMOTIVES. 


AMERICAN  COMPOUND  LOCOMOTIVES 

By  FRED  H.  COLVIN 
142  Pages  PRICE,  $1.00    Fully  Illustrated 

A  BOOK  showing  every  type  and  make  of  Compound 
Locomotives  in  use  in  the  country.  Tells  in  plain 
English — How  to  Handle  Them.  How  to  Repair  Them. 
What  to  do  if  They  Break  Down.  How  to  Disconnect 
Them.  How  to  Set  Valves.  How  to  Test  for  Leaks 
and  Locate  Blows.  All  about  Piston  Valves.  Reduc- 
ing Valves.  Valve  Motion.  Lubricating,  etc. 

CONTAINS  CHAPTERS  AS  FOLLOWS ; 

A  Bit  of  History.  Theory  of  Compounding  Steam  Cylinders. 
Baldwin  Two-Cylinder  Compound.  Pittsburg  Two-Cylinder  Com- 
pound. Rhode  Island  Compound.  Richmond  Compound.  Rogers 
Compound.  Schenectady  Two-Cylinder  Compound-  Vauclain  Com- 
pound. Tandem  Compounds.  Baldwin  Tandem.  The  Colvin-Wight- 
man  Tandem.  Schenectady  Tandem.  Balanced  Locomotives.  Bald- 
win Balanced  Compound.  Plans  for  Balancing.  Locating  Blows. 
Breakdowns.  Reducing  Valves.  Drifting.  Valve  Motion.  Discon- 
necting. Power  of  Compound  Locomotives.  Practical  Notes. 


CHARTS 


TRACTIVE  POWER  CHART 

A  chart  whereby  you  can  find  the  tractive  power  or 
drawbar  pull  of  any  locomotive,  without  making  a 
figure.  Shows  what  cylinders  are  equal,  how  driv- 
ing wheels  and  steam  pressure  affect  the  power. 
What  sized  engine  you  need  to  exert  a  given  draw- 
bar pull  or  anything  you  desire  in  this  line.  Price,  50c. 
PASSENGER  CAR  CHART 

A  chart  showing  the  anatomy  of  a  passenger  car, 
having  every  part  of  the  car  numbered  and  its 
proper  name  given  in  a  reference  list.  Price,  20c. 

BOX  CAR  CHART 

A  chart  showing  the  anatomy  of  a  box  car,  having- 
every  part  of  the  car  numbered  and  its  proper  name 
given  in  a  reference  list.    Price,  20c. 
GONDOLA  CAR  CHART 

A  chart  showing  the  anatomy  of  a  gondola  car,  hav- 
ing every  part  of  the  car  numbered  and  its  proper 
reference  name  given  in  a  reference  list.  Price,  20c. 


SIXTH  EDITION  JUST   PUBLISHED 


MACHINE  SHOP  ARITHMETIC 

By  COLVIN-  CHENEY 

145  Pages  Price,  50c.         Bound  in  Cloth 


THIS  is  an  arithmetic  of  the  things  you  have  to  do 
with  daily.  It  tells  you  plainly  about :  how  to 
find  areas  of  figures  —  how  to  find  surface  or 
volume  of  balls  or  spheres — handy  ways  for  calcula- 
ting —  about  compound  gearing  —  cutting  screw  threads 
on  any  lathe— drilling  for  taps— speeds  of  drills, 
taps,  emery  wheels,  grindstones,  milling  cutters,  etc. 
—  all  about  the  Metric  system  with  conversion  tables— 
properties  of  metals  —  strength  of  bolts  and  nuts-^ 
decimal  equivalent  of  an  inch.  All  sorts  of  machine 
shop  figuring  and  1001  other  things,  any  one  of  which 
ought  to  be  worth  more  than  the  price  of  this  book  to 
you,  as  it  saves  you  the  trouble  of  bothering  the 
boss. 


This  is  one  of  the  most  popular  Mechanical  books 
in  print.  It  contains  the  greatest  half  a  dollar's  worth  of 
information  ever  put  between  the  two  covers  of  a  book. 
Treats  on  everything  relating  to  Machine  Shop  figuring. 


JUST  PUBLISHED 

DIARY  OF  A 
ROUND  HOUSE  FOREMAN 

By  T.  S.  REILLY 

Late  Associate  Editor  "Railway  Review." 

176  PAGES  PRICE  $1.00 

'"THIS  is  the  Greatest  Book  of  Railroad  Experiences 
•*•  ever  published.  Containing  a  fund  of  information 
and  suggestions  along  the  line  of  handling  men,  organ- 
izing, etc.,  that  one  cannot  afford  to  miss.  Railroad 
men  in  any  capacity  will  thoroughly  enjoy  and  appreci- 
ate the  valuable  hints  and  funny  experiences  contained 
between  the  covers  of  this  book.  It  will  at  once  find 
a  permanent  place  in  the  library  of  all  who  want  to  get 
ahead,  as  well  as  those  who  have  climbed  the  ladder 
and  enjoy  looking  back  to  the  characters  and  times 
found  only  on  a  railroad. 

New  stories  and  laughable  experiences  are  told,  as  can  only  be 
done,  by  one  filled  with  the  sense  of  Irish  humor  and  the  power  of 
imparting  in  writing  the  humorous  incidents  connected  with  the 
knotty  problems  involved  in  every  day  life  of  a  round-house  foreman. 

While  most  of  the  suggestions  are  specifically  connected  with  the 
duties  of  a  round-house  foreman,  many  of  the  stories  are,  in  reality, 
part  of  Mr.  Reilly's  life,  obtained  while  holding  positions  of  Machin- 
ist, Round  -  House  Foreman,  Fireman,  Engineer,  Master  Mechanic 
and  Superintendent  of  Motive  Power. 

These  articles  first  appeared  serially  in  the  "  Railway  Review  " 
and  are  now  put  in  book  form,  on  account  of  the  continued  requests 
from  readers  for  them.  The  author,  a  jolly  fellow  liked  by  all,  had 
the  faculty  of  seeing  a  thread  of  fun  in  the  most  serious  of  complica- 
tions. 

An  Interesting  Book  for  Every  Railroad   Man  to 
Read  and  Profit  By. 


. 


GENERAL  LIBRARY 

umvERsrrv  OF  CAUPORNIA- 


JWJC-XVJVJtJjtl 

*N  TO  DESK  FROM  WHICH  BORROWED 

bs  book  is  due  on  the  last  date  stamped  below,  or  on  the 

date  to  which  renewed. 
Renewed  books  are  subject  to  immediate  recall. 

~  '          i ~ • 


MAY  2  01993 

JUL  2  «  1990 


RECEIVED 

NOV23«66-3p 

LOAN  DEPT. 

MAY  13 1989 

LD21-100m-l,'54(1887sl6)476 


U.C.  BERKELEY  LIBRARIES  5798" 


CDDS2b7311 


267485  <u 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


